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

extensions/racket/languages/racket/highlights.scm

@@ -4,7 +4,7 @@
  (here_string)
  (byte_string)] @string
 (regex) @string.regex
-(escape_sequence) @escape
+(escape_sequence) @string.escape
 
 [(comment)
  (block_comment)

extensions/ruby/languages/ruby/highlights.scm

@@ -116,7 +116,7 @@
 ] @string.special.symbol
 
 (regex) @string.regex
-(escape_sequence) @escape
+(escape_sequence) @string.escape
 
 [
   (integer)

extensions/scheme/languages/scheme/highlights.scm

@@ -7,7 +7,7 @@
 (symbol) @variable
 (string) @string
 
-(escape_sequence) @escape
+(escape_sequence) @string.escape
 
 [(comment)
  (block_comment)