Revert "Introduces cache to TSDB postings (#9621)"

[DylanGuedes]

This reverts commit 1221658.

What this PR does / why we need it:
We decided to discontinue the postings cache a few releases ago for not finding any evidences that postings was the culprit for the bad igw performance. Plus, we noticed a major issue with it: it doesn't bubble down shards correctly, so every query end up processing every shard.

My approach here was:

1. Revert the commit that introduced TSDB postings cache
2. Compare what changed after reverting with what we had before introducing PR 9621. If everything that changed was something introduced by PR 9621, move forward with reverting the code. Otherwise, evaluate if the change won't introduce undesired behavior
3. Delete deadcode (ex: postings_cache and codecs files)

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• CHANGELOG.md updated
  • If the change is worth mentioning in the release notes, add add-to-release-notes label
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• For Helm chart changes bump the Helm chart version in production/helm/loki/Chart.yaml and update production/helm/loki/CHANGELOG.md and production/helm/loki/README.md. Example PR
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

[owen-d]

LGTM

[grafanabot]

The backport to release-2.8.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-11157-to-release-2.8.x origin/release-2.8.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 30fbe383411c56e0d7a6be11e2333ab2513a89c0

When the conflicts are resolved, stage and commit the changes:

git add . && git cherry-pick --continue

If you have the GitHub CLI installed:

# Push the branch to GitHub:
git push --set-upstream origin backport-11157-to-release-2.8.x
# Create the PR body template
PR_BODY=$(gh pr view 11157 --json body --template 'Backport 30fbe383411c56e0d7a6be11e2333ab2513a89c0 from #11157{{ "\n\n---\n\n" }}{{ index . "body" }}')
# Create the PR on GitHub
echo "${PR_BODY}" | gh pr create --title "[release-2.8.x] Revert \"Introduces cache to TSDB postings (#9621)\"" --body-file - --label "size/XXL" --label "type/docs" --label "type/bug" --label "backport" --base release-2.8.x --milestone release-2.8.x --web

Or, if you don't have the GitHub CLI installed (we recommend you install it!):

# Push the branch to GitHub:
git push --set-upstream origin backport-11157-to-release-2.8.x

# Create a pull request where the `base` branch is `release-2.8.x` and the `compare`/`head` branch is `backport-11157-to-release-2.8.x`.

# Remove the local backport branch
git switch main
git branch -D backport-11157-to-release-2.8.x

[grafanabot]

The backport to release-2.9.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-11157-to-release-2.9.x origin/release-2.9.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 30fbe383411c56e0d7a6be11e2333ab2513a89c0

When the conflicts are resolved, stage and commit the changes:

git add . && git cherry-pick --continue

If you have the GitHub CLI installed:

# Push the branch to GitHub:
git push --set-upstream origin backport-11157-to-release-2.9.x
# Create the PR body template
PR_BODY=$(gh pr view 11157 --json body --template 'Backport 30fbe383411c56e0d7a6be11e2333ab2513a89c0 from #11157{{ "\n\n---\n\n" }}{{ index . "body" }}')
# Create the PR on GitHub
echo "${PR_BODY}" | gh pr create --title "[release-2.9.x] Revert \"Introduces cache to TSDB postings (#9621)\"" --body-file - --label "size/XXL" --label "type/docs" --label "type/bug" --label "backport" --base release-2.9.x --milestone release-2.9.x --web

Or, if you don't have the GitHub CLI installed (we recommend you install it!):

# Push the branch to GitHub:
git push --set-upstream origin backport-11157-to-release-2.9.x

# Create a pull request where the `base` branch is `release-2.9.x` and the `compare`/`head` branch is `backport-11157-to-release-2.9.x`.

# Remove the local backport branch
git switch main
git branch -D backport-11157-to-release-2.9.x

[grafanabot]

The backport to k174 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-11157-to-k174 origin/k174
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 30fbe383411c56e0d7a6be11e2333ab2513a89c0

When the conflicts are resolved, stage and commit the changes:

git add . && git cherry-pick --continue

If you have the GitHub CLI installed:

# Push the branch to GitHub:
git push --set-upstream origin backport-11157-to-k174
# Create the PR body template
PR_BODY=$(gh pr view 11157 --json body --template 'Backport 30fbe383411c56e0d7a6be11e2333ab2513a89c0 from #11157{{ "\n\n---\n\n" }}{{ index . "body" }}')
# Create the PR on GitHub
echo "${PR_BODY}" | gh pr create --title "[k174] Revert \"Introduces cache to TSDB postings (#9621)\"" --body-file - --label "size/XXL" --label "type/docs" --label "type/bug" --label "backport" --base k174 --milestone k174 --web

Or, if you don't have the GitHub CLI installed (we recommend you install it!):

# Push the branch to GitHub:
git push --set-upstream origin backport-11157-to-k174

# Create a pull request where the `base` branch is `k174` and the `compare`/`head` branch is `backport-11157-to-k174`.

# Remove the local backport branch
git switch main
git branch -D backport-11157-to-k174