Summary:
Originally, there were two gflags/gucs yb_enable_ash and yb_ash_enable_infra.

yb_ash_enable_infra was responsible for one-time things like allocating shared
memory, starting the ASH collector bg worker, attaching the executor hooks.
yb_enable_ash was responsible for collection of events, sending ASH metadata
along with RPCs.

It doesn't make much sense for yb_enable_ash to be false while
yb_ash_enable_infra is true, as the collector would still be running but it won't be
doing anything. This diff deprecates yb_ash_enable_infra, and now
yb_enable_ash is also responsible for the one-time things.

This diff also updates ysql_yb_enable_ash to a non-preview non-runtime flag.
Jira: DB-14313

Test Plan: Jenkins

Reviewers: jason, hsunder, amitanand, hbhanawat

Reviewed By: jason, hsunder

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D40424