refactor(regular_expression)!: Simplify public APIs

[leaysgur]

This PR makes 2 changes to improve the existing API that are not very useful.

• Remove (Literal)Parser and FlagsParser and their ASTs
• Add with_flags(flags_text) helper to ParserOptions

Here are the details.

Remove (Literal)Parser and FlagsParser and their ASTs

Previously, the oxc_regular_expression crate exposed 3 parsers.

• (Literal)Parser: assumes /pattern/flags format
• PatternParser: assumes pattern part only
• FlagsParser: assumes flags part only

However, it turns out that in actual usecases, only the PatternParser is actually sufficient, as the pattern and flags are validated and sliced in advance on the oxc_parser side.

The current usecase for (Literal)Parser is mostly for internal testing.

There were also some misuses of (Literal)Parser that restore format!("/{pattern}/{flags}") back and use (Literal)Parser.

Therefore, only PatternParser is now published, and unnecessary ASTs have been removed.
(This also obsoletes #5592 .)

Added with_flags(flags_text) helper to ParserOptions

Strictly speaking, there was a subtle difference between the "flag" strings that users were aware of and the "mode" recognised by the parser.

Therefore, it was a common mistake to forget to enable unicode_mode when using the v flag.

With this helper, crate users no longer need to distinguish between flags and modes.

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[codspeed-hq]

CodSpeed Performance Report

Merging #6262 will not alter performance

_{Comparing issue-6141-pre2 (5a73a66) with main (5957214)}

Summary

✅ 29 untouched benchmarks

[Boshen]

BEAUTIFUL!

[graphite-app]

Merge activity

• Oct 2, 10:46 PM EDT: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Oct 2, 10:46 PM EDT: Boshen added this pull request to the Graphite merge queue.
• Oct 2, 10:51 PM EDT: Boshen merged this pull request with the Graphite merge queue.