[PROPOSAL/SURVEY] Enable background cleanup for state with TTL by default

[Andrey Zagrebin <az...@apache.org>]

Hi all,

We were thinking about enabling background cleanup for the state with TTL
by default:
StateTtlConfig#Builder#cleanupInBackground()

Previously, we did not have it in the first implementation of TTL if you
remember.
So technically, we were a bit conservative to not enable it by default at
once.
In general, most of TTL use cases should always enable background cleanup
one way or another,
because it is usually needed. It means that it makes sense to enable it for
users to not care about it by default.

I am starting this thread to collect any feedback for this change which we
want to include into 1.10 release. Basically, the question is whether there
have been any problems with the background cleanups to postpone this change.

JIRA issue and PR:
https://issues.apache.org/jira/browse/FLINK-14898

I will let the thread to hang for some time if nothing speaks against it we
will merge it next week and include into 1.10.

Thanks,
Andrey