perf(eventstore): optimize commands to events function (#9092)

# Which Problems Are Solved

We were seeing high query costs in a the lateral join executed in the
commands_to_events procedural function in the database. The high cost
resulted in incremental CPU usage as a load test continued and less
req/sec handled, sarting at 836 and ending at 130 req/sec.

# How the Problems Are Solved

1. Set `PARALLEL SAFE`. I noticed that this option defaults to `UNSAFE`.
But it's actually safe if the function doesn't `INSERT`
2. Set the returned `ROWS 10` parameter.
3. Function is re-written in Pl/PgSQL so that we eliminate expensive
joins.
4. Introduced an intermediate state that does `SELECT DISTINCT` for the
aggregate so that we don't have to do an expensive lateral join.

# Additional Changes

Use a `COALESCE` to get the owner from the last event, instead of a
`CASE` switch.

# Additional Context

- Function was introduced in
https://github.com/zitadel/zitadel/pull/8816
- Closes https://github.com/zitadel/zitadel/issues/8352

---------

Co-authored-by: Silvan <27845747+adlerhurst@users.noreply.github.com>

cmd/setup/40.go

@@ -48,5 +48,5 @@ func (mig *InitPushFunc) Execute(ctx context.Context, _ eventstore.Event) (err e
 }
 
 func (mig *InitPushFunc) String() string {
-	return "40_init_push_func"
+	return "40_init_push_func_v2"
 }