Add Buildifier

[furtib]

Why:
We want to lint not just our Python but also our .bzl files.

What:

• Add buildifier_prebuilt as a bazel dependency
• Create test rule for buildifier_prebuilt

Addresses:
#155

[furtib]

Sorry, I messed up the previous PR.
We were in a state where the output was illegible, and I tried a couple of things to improve readability.

I tried my best to find a more legible output format.
The best so far is instead of checking the logs, looking at the summary tab under the action. (I somehow even got syntax highlighting to work there, at the cost of having to run buildifier a third time, the first 2 are unavoidable)

[furtib]

I'm rebasing the formatting PR to this.
To see the formatter warnings, see:
https://github.com/Ericsson/codechecker_bazel/actions/runs/21643464278/job/62389195527?pr=187

[furtib]

If it were to pass, this would be the most solid option.
I will look for a way to do the same with pylint and so on.
If that is possible, we might not even need a separate job, since linting will be run with bazel test ....