Add node generation and proactive expiration policies

[maypok86]

Description

Added node generation and proactive expiration policies:

• Disabled
• Fixed (queue)
• Variable (timer wheel)

Related issue(s)

• Resolves Node generation #55

✅ Checklist for your Pull Request

Related changes (conditional)

• Tests

  • If I added new functionality, I added tests covering it.
  • If I fixed a bug, I added a regression test to prevent the bug from
    silently reappearing again.

• Documentation

  • I checked whether I should update the docs and did so if necessary:
    • README

• Public contracts

  • My changes doesn't break project license.

Stylistic guide (mandatory)

• My code complies with the styles guide.

• My commit history is clean (only contains changes relating to my
  issue/pull request and no reverted-my-earlier-commit changes) and commit
  messages start with identifiers of related issues in square brackets.

  Example: [#42] Short commit description

  If necessary both of these can be achieved even after the commits have been
  made/pushed using rebase and squash.

Before merging (mandatory)

• Check target branch of PR is set correctly

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 96.82540% with 10 lines in your changes are missing coverage. Please review.

Project coverage is 95.37%. Comparing base (b0df6d5) to head (d25b87e).

Files	Patch %	Lines
internal/core/cache.go	95.91%	2 Missing ⚠️
internal/expire/disabled.go	71.42%	2 Missing ⚠️
internal/expire/queue.go	95.00%	1 Missing and 1 partial ⚠️
internal/expire/variable.go	97.64%	1 Missing and 1 partial ⚠️
internal/s3fifo/queue.go	95.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #58      +/-   ##
==========================================
- Coverage   95.64%   95.37%   -0.28%     
==========================================
  Files          20       22       +2     
  Lines        1194     1232      +38     
==========================================
+ Hits         1142     1175      +33     
- Misses         35       39       +4     
- Partials       17       18       +1     

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