chore(vector-core): remove blanket allows

[hjooh]

Summary

Removes two blanket #![allow(...)] attributes from lib/vector-core/src/lib.rs:

• clippy::cast_possible_wrap
• clippy::cast_sign_loss

These two statements were suppressing lints across the entire vector-core crate. The contents of this PR replace them with specific suppressions at 6 locations (comments with justification/explanations were also modified or added at each location).

Vector configuration

N/A (no behavior changes).

How did you test this PR?

• make check-clippy passes
• make check-fmt passes
• cargo vdev test: 3002/3005 tests pass, 3 failures seemed to be preexisting environment related issues unrelated to this change

Change Type

• Bug fix
• New feature
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

Related: #23659

Notes

• Please read our Vector contributor resources.
• Do not hesitate to use @vectordotdev/vector to reach out to us regarding this PR.
• Some CI checks run only after we manually approve them.
  • We recommend adding a pre-push hook, please see this template.
  • Alternatively, we recommend running the following locally before pushing to the remote branch:
    • make fmt
    • make check-clippy (if there are failures it's possible some of them can be fixed with make clippy-fix)
    • make test
• After a review is requested, please avoid force pushes to help us review incrementally.
  • Feel free to push as many commits as you want. They will be squashed into one before merging.
  • For example, you can run git merge origin master and git push.
• If this PR introduces changes Vector dependencies (modifies Cargo.lock), please
  run make build-licenses to regenerate the license inventory and commit the changes (if any). More details on the dd-rust-license-tool.

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[hjooh]

I have read the CLA Document and I hereby sign the CLA

[hjooh]

recheck