Add approvals to get_merge_request tool.

Note

Before picking up this work: this issue adds an MCP tool. Please follow the Adding a new tool guidance first. That includes creating an MCP Tool Proposal, using verb_object naming (get_ / list_ / save_ / delete_), and the shared resource-identification input base classes.

Proposal

Rather than implementing a new tool to get Merge request approvals those should be part of the get_merge_request tool.

Multiple options exist that should be evaluated based on ease of implementation and the underlying data structure:

1. Add a new facet (like commits/discussions)
2. Include it by default as part of the main MR payload
3. Include it as part of an existing facet / adjust facets (e.g. review)

Parent Epic: &20529 (closed)