Auto merge of #7442 - camsteffen:format-args, r=xFrednet

Auto merge of #7442 - camsteffen:format-args, r=xFrednet

Refactor `format_args!` expansion parsing

Introduces `FormatExpn::parse` and `FormatArgsExpn::parse`. Motivated by rust-lang/rust#83302, so I only have to change Clippy in one place. Fixed an FP along the way.

I also allowed `needless_bool` in macros because I often want to do `if_chain! { .. then { true } else { false } }`.

changelog: Fix false positive in `useless_format` when some text is appended or prepended to a single string with some useless formatting params
changelog: Allow `needless_bool` in macros