storage controller: register nodes in re-attach request (#7040)

## Problem

Currently we manually register nodes with the storage controller, and
use a script during deploy to register with the cloud control plane.
Rather than extend that script further, nodes should just register on
startup.

## Summary of changes

- Extend the re-attach request to include an optional
NodeRegisterRequest
- If the `register` field is set, handle it like a normal node
registration before executing the normal re-attach work.
- Update tests/neon_local that used to rely on doing an explicit
register step that could be enabled/disabled.

---------

Co-authored-by: Christian Schwarz <christian@neon.tech>

test_runner/regress/test_compatibility.py

@@ -242,7 +242,7 @@ def test_forward_compatibility(
         # everything else: our test code is written for latest CLI args.
         env.neon_local_binpath = neon_local_binpath
 
-        neon_env_builder.start()
+        neon_env_builder.start(register_pageservers=True)
 
         check_neon_works(
             env,