agent2: Port read_file tool (#35840)

Ports the read_file tool from `assistant_tools` to `agent2`. 

Note: Image support not implemented.

Release Notes:

- N/A
3d662ee282Agus Zubiaga committed on 8/7/2025, 11:46:47 PM· committed by GitHubparent7d4d8b8
6 files changedLine totals unavailable