Add new lint `octal_escapes`
This checks for sequences in strings that would be octal character
escapes in C, but are not supported in Rust. It suggests either
to use the `\x00` escape, or an equivalent hex escape if the octal
was intended.
Fixes#7981
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changelog: Add new lint [`octal_escapes`], which checks for literals like `"\033[0m"`.
57a8804ef9