Add `format_in_format_args` and `to_string_in_format_args` lints
Fixes#7667 and #7729
I put these in `perf` since that was one of `@jplatte's` suggestions, and `redundant_clone` (which I consider to be similar) lives there as well.
However, I am open to changing the category or anything else.
r? `@camsteffen`
changelog: Add `format_in_format_args` and `to_string_in_format_args` lints