Format `type: ignore` comments

[KotlinIsland]

Type ignore comments are standard constructs in python code. I think it would be based if black formatted them.

a: SUS = "AMONGUS" + 1  # type:ignore     [   name-defined      ,    operator     ,misc    ]

Could be formatted to:

a: SUS = "AMONGUS" + 1  # type: ignore[name-defined, operator, misc]

[isidentical]

Just a side note: beside simply putting a single whitespace after the separator (since trailing white-space is ignored by the python tokenizer, #type: ignore and #type:ignore is basically the same thing in the AST), anything else would change the AST.

[JelleZijlstra]

Yes, everything after the ignore has only implementation-defined meaning. I suppose we could format assuming mypy semantics, though.

[KotlinIsland]

PyCharm assumes mypy semantics

[cobaltt7]

Part of this is implemented in #4645 (Excess spaces after the # and : are removed, but the value is left unchanged). IMO, the value shouldn't be changed for the reasons mentioned here: there's only implementation-defined meaning and we would have to assume mypy semantics, and the AST safety check would have to be modified for this case. Please share your thoughts.