Replica promote (#12090)

## Problem

This PR is part of larger computes support activity:

https://www.notion.so/neondatabase/Larger-computes-114f189e00478080ba01e8651ab7da90

Epic: https://github.com/neondatabase/cloud/issues/19010

In case of planned node restart, we are going to 
1. create new read-only replica
2. capture LFC state at primary
3. use this state to prewarm replica
4. stop old primary
5. promote replica to primary

Steps 1-3 are currently implemented and support from compute side.
This PR provides compute level implementation of replica promotion.

Support replica promotion

## Summary of changes

Right now replica promotion is done in three steps:
1. Set safekeepers list (now it is empty for replica)
2. Call `pg_promote()` top promote replica
3. Update endpoint setting to that it ids not more treated as replica.

May be all this three steps should be done by some function in
compute_ctl. But right now this logic is only implement5ed in test.

Postgres submodules PRs:
https://github.com/neondatabase/postgres/pull/648
https://github.com/neondatabase/postgres/pull/649
https://github.com/neondatabase/postgres/pull/650
https://github.com/neondatabase/postgres/pull/651

---------

Co-authored-by: Matthias van de Meent <matthias@neon.tech>
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>

test_runner/fixtures/neon_fixtures.py

@@ -4711,7 +4711,7 @@ class EndpointFactory:
         origin: Endpoint,
         endpoint_id: str | None = None,
         config_lines: list[str] | None = None,
-    ):
+    ) -> Endpoint:
         branch_name = origin.branch_name
         assert origin in self.endpoints
         assert branch_name is not None
@@ -4730,7 +4730,7 @@ class EndpointFactory:
         origin: Endpoint,
         endpoint_id: str | None = None,
         config_lines: list[str] | None = None,
-    ):
+    ) -> Endpoint:
         branch_name = origin.branch_name
         assert origin in self.endpoints
         assert branch_name is not None