1. Adds local-proxy to compute image and vm spec
2. Updates local-proxy config processing, writing PID to a file eagerly
3. Updates compute-ctl to understand local proxy compute spec and to
send SIGHUP to local-proxy over that pid.
closes https://github.com/neondatabase/cloud/issues/16867
```shell
$ cargo run -p proxy --bin proxy -- --auth-backend=web --webauth-confirmation-timeout=5s
```
```
$ psql -h localhost -p 4432
NOTICE: Welcome to Neon!
Authenticate by visiting within 5s:
http://localhost:3000/psql_session/e946900c8a9bc6e9
psql: error: connection to server at "localhost" (::1), port 4432 failed: Connection refused
Is the server running on that host and accepting TCP/IP connections?
connection to server at "localhost" (127.0.0.1), port 4432 failed: ERROR: Disconnected due to inactivity after 5s.
```
Add binary for local-proxy that uses the local auth backend. Runs only
the http serverless driver support and offers config reload based on a
config file and SIGHUP