proxy: add local-proxy to compute image

[conradludgate]

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

[github-actions]

5085 tests run: 4878 passed, 0 failed, 207 skipped (full report)

---

Flaky tests (4)

Postgres 17

• test_multixid_wraparound_import: release-x86-64

Postgres 16

• test_node_status_after_restart: release-x86-64
• test_subscriber_restart: release-x86-64

Postgres 14

• test_storage_controller_compute_hook: release-x86-64

Code coverage* (full report)

• functions: 31.4% (7509 of 23942 functions)
• lines: 49.6% (60273 of 121590 lines)

* collected from Rust tests only

---

_{The comment gets automatically updated with the latest test results
f119dc4 at 2024-10-04T13:36:41.362Z :recycle:}