The PR cleans up unnecessary loop variable copying and enables the
[`copyloopvar`](https://golangci-lint.run/usage/linters/#copyloopvar)
linter for detecting this redundant variable copying.
#### Additional notes
After the project upgraded to Go version 1.22 in #4779, copying
variables inside a `for` loop became unnecessary. See this [blog
post](https://go.dev/blog/loopvar-preview) for a detailed explanation.
The `copyloopvar` linter is only available from `golangci-lint` v1.57
onwards, so we also need to update this tool.
00a376cc64