feat: Add support for GitHub Projects v2 Iteration Fields

[joaodotwork]

This PR implements support for GitHub Projects v2 Iteration Fields, addressing the feature request in #1854.

It adds the following tools:

• create_project: Allows creating a new GitHub Project (Projects V2).
• create_iteration_field: Allows creating and configuring an Iteration field (sprints) on a project, including defining the start date and duration.

These additions enable AI agents to automate sprint planning workflows by creating projects and setting up iteration cycles programmatically.

The implementation uses the githubv4 GraphQL client to perform the necessary mutations (createProjectV2, createProjectV2Field, updateProjectV2Field).

Closes #1854

[SamMorrowDrums]

Hey @joaodotwork interested in potentially merging PR, but there's a merge conflict and there was a couple of other changes to projects tools, including removal of old ones, so please give another check and fix merge conflicts and one of us will review after.

[joaodotwork]

thanks Sam! will do ✊🏽

[SamMorrowDrums]

@joaodotwork apologies for slow response!

I appreciate all the updates, things are just constantly crazy at the moment.

I will reopen if it's ok.

[SamMorrowDrums]

Closing in favor of a new PR that consolidates these tools into the existing projects_write tool as new methods (create_project and create_iteration_field), following the consolidated pattern used by projects_list/projects_get/projects_write. The iterations parameter is now optional, and CI issues (gosec G115) are fixed. Thank you @joaodotwork for the original contribution — you're credited as co-author in the new PR.

[joaodotwork]

so happy @SamMorrowDrums !