Add direct include needed for absl::StrCat

[hershi]

Before this was used without a direct include statement, which relies on a transitive include to bring it into scope and can easily break... which it does with one of the more up-to-date versions of absl. This fix should help avoid breakages when we want to update the abseil dependency

Repro:

• Add the following to the WORKSPACE

git_repository(
  name = "com_google_absl",
  remote = "https://github.com/abseil/abseil-cpp",
  commit = "27478af36914f18867ea32cb42db00dba15fffcd",
)

• bazel build src/main/cc/any_sketch:any_sketch - errors out
  • After the fix, builds successfully

[wfa-reviewable]

This change is 

[SanjayVas]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @hershi)

a discussion (no related file):
Thank you for the contribution!

---

[hershi]

@SanjayVas is there any follow up action needed on me? Since I don't have write access I can't merge this :)

Also, lint seems to have failed due to an infra issue, not if it needs to be re-run and how

Error: ReserveCacheError: Unable to reserve cache with key ktlint-0.40.0, another job may be creating this cache.

[SanjayVas]

@SanjayVas is there any follow up action needed on me? Since I don't have write access I can't merge this :)

I'll go ahead and merge.

Also, lint seems to have failed due to an infra issue, not if it needs to be re-run and how

Error: ReserveCacheError: Unable to reserve cache with key ktlint-0.40.0, another job may be creating this cache.

Re-run worked. I think this repo is using some old GitHub Action versions that have some flakiness. Will update in a separate PR.