c-ares: disable shared resolver by default

[andy-fong]

Commit Message: c-ares: disable shared resolver by default
Additional Description:
DnsFilter would call createDnsResolver() from a workerthread that would cause a race when sharing dns resolvers.
Turn off this feature until the race is fixed. Relates to #46577 and #45073
Risk Level: low
Testing:
Docs Changes:
Release Notes:
Platform Specific Features:

[repokitteh-read-only]

CC @envoyproxy/runtime-guard-changes: FYI only for changes made to (source/common/runtime/runtime_features.cc).

🐱

Caused by: #46622 was opened by andy-fong.

see: more, trace.

[andy-fong]

@yanjunxiang-google @tonya11en please take a look. This is exactly the same as #46585 but against main.
I have a fix to move the sharing into the cluster instead of doing it in the dns_resolver so it won't affect any filters creating dns resolver. I still need to do some final testing and will post the PR tomorrow. The change is not big at all but expect it might take sometime to get it review and merge. I also switch the default to false with the fix because of the other use case I mentioned in the origin PR. So, it's still good to get this merged and backport to 1.39.x to stop anyone hitting this bug.

[andy-fong]

The checks failure seems to be unrelated to this change.

[andy-fong]

I created the full fix PR #46657 which will supersede this but if that PR takes sometimes to review, it's good to merge this first and backport to 1.39.x branch to stop the bug.

[yanjunxiang-google]

LGTM

[yanjunxiang-google]

/retest