[tracker] flake8-bugbear progression

[ShadowJonathan]

This is a tracker issue for adding flake8-bugbear in short steps, and to keep track of it's progress.

The original PR was #9320, it has been split in the following PRs;

• Add flake8-bugbear dependency, put B00 in ignore list, and fix remaining violations (Add bugbear, add B00 to ignored checks, and fix 2 violation codes #9499)
• Finish check-fixing PRs (in order of altering ignore keys):
  • B00 -> B006,B007,B008: Add more bugbear codes #9659
  • B006,B007,B008 -> B007: Bugbear: Add Mutable Parameter fixes #9682
  • B007 -> "": Fix (final) Bugbear violations #9838
• Discuss and merge making flake8 explicitly select checks (issue #XXXX, PR #XXXX)
  • Add one B code on select= (#XXXX)
  • Enable opinionated checks (B90) (#XXXX)
• (Side-quest) Update bugbear to 21.4 (which adds a new check) (#XXXX)

(Some more information in #9279 about some specifics of these checks)

(#9370 was originally part of this tracker issue, but was denied, some discussion followed)

[ShadowJonathan]

Optionally i'd also like to enable B90, (as said in #9279), or a select few of these checks, these can happen after the second PR, but just to note that.

[ShadowJonathan]

(made #9368 and #9369 to be deliberated for after the first PR)

[clokep]

@ShadowJonathan Looks like a lot of this is done! 🎉 Any update on here that we should add?

[ShadowJonathan]

Already added all those updates, next step is "Discuss and merge making flake8 explicitly select checks", i'll make a properly-worded Process issue for that whenever i have time, currently bugbear is "there", but i'd like to also enable some of those "opinionated" checks.

Additionally, I'd wanna update bugbear to the latest version, to fix the newest checks that were added, lemme add that one now...