Implement metadata finder for pre-commit

[AbhishekBhaskar]

What are you trying to accomplish?

This PR implements the MetadataFinder class for pre-commit.

• Pre-commit dependencies use the repo URL as the dependency name (e.g., https://github.com/pre-commit/pre-commit-hooks)
• The source is stored in requirements with type: "git" and has a url field

Anything you want to highlight for special attention from reviewers?

The implementation mirrors the github_actions pattern but accounts for pre_commit's URL-based naming convention

How will you know you've accomplished your goal?

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.

[Copilot]

Pull request overview

This PR implements the MetadataFinder class for the pre-commit ecosystem, enabling Dependabot to discover source repositories, changelogs, and release notes for pre-commit hooks.

Changes:

• Implements MetadataFinder#look_up_source to extract source URLs from pre-commit dependencies
• Handles both GitHub and GitLab sources
• Supports subdependencies (dependencies with no requirements) by using the dependency name directly as the URL
• Follows the established pattern from github_actions ecosystem

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
pre_commit/lib/dependabot/pre_commit/metadata_finder.rb	Implements MetadataFinder class with look_up_source method that extracts URLs from dependency requirements or uses dependency name for subdependencies
pre_commit/spec/dependabot/pre_commit/metadata_finder_spec.rb	Adds comprehensive test coverage for GitHub sources, GitLab sources, and subdependencies with no requirements