[Bug]: The UI issues many API requests when stopping multiple runs

[r4victor]

Steps to reproduce

1. Submit multiple runs (e.g. 20 runs).
2. Open http://localhost:8000/runs, choose all runs and stop them.
3. Check that browser sends a separate request to /api/project/{project_name}/runs/stop for each run.

This creates unnecessary load on the server (and may lead to "database is locked" with SQLite). The UI should make a single request to such endpoints. The stop endpoint supports passing multiple runs. The same applies for other endpoints (e.g. delete volumes).

Actual behaviour

No response

Expected behaviour

No response

dstack version

master

Server logs

No response

Additional information

No response