[DocDB] Seperate the cache expiration timeout for successful and failed DNS resolutions.

[lingamsandeep]

Jira Link: DB-11222

Description

Currently the GFlag - FLAG_dns_cache_expiration_ms controls the duration for which DNS resolution result is cached for both on success and failure.

However it may be desirable to cache a failure entry for much shorter so that resolution can be reattempted sooner.

Issue Type

kind/bug

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