feat(compute): Introduce privileged_role_name parameter (#12539)

## Problem

Currently `neon_superuser` is hardcoded in many places. It makes it
harder to reuse the same code in different envs.

## Summary of changes

Parametrize `neon_superuser` in `compute_ctl` via
`--privileged-role-name` and in `neon` extensions via
`neon.privileged_role_name`, so it's now possible to use different
'superuser' role names if needed. Everything still defaults to
`neon_superuser`, so no control plane code changes are needed and I
intentionally do not touch regression and migrations tests.

Postgres PRs:
- https://github.com/neondatabase/postgres/pull/674
- https://github.com/neondatabase/postgres/pull/675
- https://github.com/neondatabase/postgres/pull/676
- https://github.com/neondatabase/postgres/pull/677

Cloud PR:
- https://github.com/neondatabase/cloud/pull/31138

vendor/revisions.json

@@ -1,18 +1,18 @@
 {
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     "17.5",
-    "353c725b0c76cc82b15af21d8360d03391dc6814"
+    "8de764e44b56d1cffb3644368d4d689f482b611a"
   ],
   "v16": [
     "16.9",
-    "e08c8d5f1576ca0487d14d154510499c5f12adfb"
+    "c148871eada02c0cf15d553d8ff7c389d01810f2"
   ],
   "v15": [
     "15.13",
-    "afd46987f3da50c9146a8aa59380052df0862c06"
+    "21cb86b81454522870d3634cac3e10b821da09fe"
   ],
   "v14": [
     "14.18",
-    "8ce1f52303aec29e098309347b57c01a1962e221"
+    "af550a80c6b86d0fec378ee929e2bb2e591e5cd3"
   ]
 }