chore(linter): Fix issues flagged by updated golangci-lint version

[sophiewaldman]

What this PR does / why we need it:
Fix issues flagged by the updated golangci-lint version. Lots of changes but all individually small and straightforward.

Which issue(s) this PR fixes:
Prerequisite for #18623

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• 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

[paul1r]

lgtm, thank you!

[loki-gh-app]

Hello @trevorwhitney!
Backport pull requests need to be either:

• Pull requests which address bugs,
• Urgent fixes which need product approval, in order to get merged,
• Docs changes.

Please, if the current pull request addresses a bug fix, label it with the type/bug label.
If it already has the product approval, please add the product-approved label. For docs changes, please add the type/docs label.
If the pull request modifies CI behaviour, please add the type/ci label.
If none of the above applies, please consider removing the backport label and target the next major/minor release.
Thanks!

[loki-gh-app]

The backport to release-3.5.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-19206-to-release-3.5.x origin/release-3.5.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 98b411a6491781447c82992715711c239a8df74a

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-19206-to-release-3.5.x
# Create the PR body template
PR_BODY=$(gh pr view 19206 --json body --template 'Backport 98b411a6491781447c82992715711c239a8df74a from #19206{{ "\n\n---\n\n" }}{{ index . "body" }}')
# Create the PR on GitHub
echo "${PR_BODY}" | gh pr create --title 'chore(linter): Fix issues flagged by updated golangci-lint version (backport release-3.5.x)' --body-file - --label 'size/XL' --label 'product-approved' --label 'backport' --base release-3.5.x --milestone release-3.5.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-19206-to-release-3.5.x

# Create a pull request where the `base` branch is `release-3.5.x` and the `compare`/`head` branch is `backport-19206-to-release-3.5.x`.

# Remove the local backport branch
git switch main
git branch -D backport-19206-to-release-3.5.x