Improve syntax highlights (#18728)

Closes #18722

- Replace the `@escape` capture name with `@string.escape` for escape
sequences in Go, Python, Regex, Racket, Ruby, and Scheme.
- Rust
  - Add syntax highlighting for escape sequences. Close #18722
- Fix the issue where `@punctuation.delimiter` is being overwritten by
`@operator`.
  - Add the period (".") to `@punctuation.delimiter`.

Release Notes:

- N/A

crates/languages/src/regex/highlights.scm

@@ -22,7 +22,7 @@
   (end_assertion)
   (boundary_assertion)
   (non_boundary_assertion)
-] @escape
+] @string.escape
 
 [
   "*"