GitHub: Register Pull Request Operation Tools

[vudayani]

Description

This PR adds the registration of tools to enhance pull request operations in the GitHub MCP server.

The following tools are registered:

list_pull_requests: List and filter pull requests in a GitHub repository
get_pull_request: Retrieve details of a specific pull request in a GitHub repository
get_pull_request_status: Get the combined status of all checks for a pull request
get_pull_request_files: Fetch the list of files changed in a pull request

Server Details

• Server: github
• Changes to: tools

Motivation and Context

• Greatly enhances the usability of the server by providing critical pull request-related operations
• Helps automate workflows and provides better support for managing GitHub pull requests

How Has This Been Tested?

The tools have been tested against GitHub repositories in the following scenarios:

• Listing pull requests with various filters applied
• Fetching details of individual pull requests
• Retrieving status checks for pull requests
• Fetching files changed in pull requests

Breaking Changes

• No breaking changes as this is a non-disruptive addition of new tools
• No changes are required to existing MCP configurations

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Protocol Documentation
• My changes follows MCP security best practices
• I have updated the server's README accordingly
• I have tested this with an LLM client
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have documented all environment variables and configuration options

Additional context