docs: add PPL rex and regex commands report for v3.3.0

[tkykenmt]

Summary

This PR adds documentation for the new PPL regex and rex commands introduced in OpenSearch v3.3.0.

Reports Created

• Release report: docs/releases/v3.3.0/features/sql/ppl-rex-and-regex-commands.md
• Feature report: docs/features/sql/ppl-rex-and-regex-commands.md

Key Changes in v3.3.0

regex command:

• Pattern-based filtering using Java regex
• Supports positive (=) and negative (!=) matching
• Case-sensitive by default with inline flag support

rex command:

• Field extraction using named capture groups
• Multi-value extraction with max_match parameter
• Text transformation with mode=sed
• Position tracking with offset_field

Related PRs

• #4083: Implementation of regex command
• #4109: Core implementation of rex command
• #4241: Implementation of sed mode and offset_field

Closes #1330