feat: add regexp metadata extraction step

[NoeFlandre]

Description

This PR introduces a new regexp method for the metadata step, allowing users to extract metadata using regular expressions.

It also includes a bug fix in synda/model/step.py to correctly handle Annotated types using TypeAdapter during step configuration validation.

Changes

• Config: Added Regexp and RegexpParameters models.
• Pipeline: Implemented Regexp executor with regex search logic and progress tracking.
• Bug Fix: Updated Step.get_step_config to use TypeAdapter for metadata steps.

Verification

Verified with a manual smoke test using a CSV source and regex pattern for emails.

• Successfully extracted email addresses with correct start/end offsets.
• Verified progress bar UI and CSV output.