Add edit_pr tool with clear message about not pushing code changes

[codegen-sh]

This PR adds the edit_pr tool with a clear message about not pushing code changes to the PR branch.

Key changes:

1. Created a new edit_pr.py file with a clear message in the observation that states:

   "Successfully updated PR #{pr_number} ({', '.join(updates)}). Note that this tool only updates PR metadata and does not push code changes to the PR branch. To add code changes to a PR, make your edits and then use the `create_pr` tool while on the PR branch."
   

2. Added the GithubEditPRTool class to the tools.py file with a descriptive name and documentation
3. Added GithubEditPRTool, GithubViewPRCheckTool, and GithubCheckoutPRTool to the get_workspace_tools function
4. Fixed the GithubViewPRCheckTool class to use the correct input schema

These changes ensure that all the GitHub PR-related tools are properly registered and available for use, and that users are clearly informed that the edit_pr tool only updates metadata and not code changes.