### Summary

This adds some plugin utilities, mainly to support `stripe projects`:

- Add support for plugins to run some logic during `stripe plugins
install`/`upgrade`/`uninstall`. This fails open so that install,
upgrade, and uninstall can still proceed if the logic fails or is
unimplemented.
- Add a `SwitchContext` rpc for plugins to call, which does the same
thing as `stripe switch context`.
- Support passing the `--access-base`, `--api-base`, and
`--dashboard-base` values from core to plugin, mainly for better DX
since these aren't user facing.

### Testing

For the install hooks, I tested it doesn't break the existing behavior.
We should test the actual end-to-end flow once there's a plugin
implementing these.

<img width="788" height="88" alt="Screenshot 2026-08-31 at 11 39 26 AM"
src="https://github.com/user-attachments/assets/aa264fa0-41f4-4198-9dd0-c95e1cc9b0cd"
/>

<img width="669" height="103" alt="Screenshot 2026-08-31 at 11 47 50 AM"
src="https://github.com/user-attachments/assets/2244644d-36a4-4430-a103-a8ab4d26ab5b"
/>

For the SwitchContext rpc, I tested the `stripe switch context` command
still works. Again, we should test this with a real plugin at some
point.

<img width="693" height="63" alt="Screenshot 2026-08-31 at 11 59 50 AM"
src="https://github.com/user-attachments/assets/1d0a7b8d-14e0-440e-94ec-84621a10d023"
/>

For the base URLs, I tested this with a dummy command in projects:

<img width="1272" height="130" alt="Screenshot 2026-08-31 at 2 40 09 PM"
src="https://github.com/user-attachments/assets/8c963478-f98b-4636-bc45-009d8b08ab82"
/>

---------

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>