Linting: lint more on new code only

[qdm12]

Why this should be merged

Have impactful linting only on new code, for both the CI and locally.
I thought about it as it can be useful to learn how to write better Go code.
Should be applied to other repositories too ideally.

How this works

• CI only lints new issues, see [this](See https://github.com/golangci/golangci-lint-action?tab=readme-ov-file#only-new-issues) - works for both PRs and branch commits
• Local linting only lints new issues, see the --new flag in https://golangci-lint.run/usage/configuration/#command-line-options)
• Remove unused and unneeded configuration options
• Add a bunch of linters I personally use - happy to customize their settings or remove some if they prove to be annoying - don't forget you can use //nolint:linter-name in case to disable the linter on a single line.

How this was tested

• Linter passing locally
• CI passing

Need to be documented?

No

Need to update RELEASES.md?

No