Make the resolver retry timeout configurable via __res_params

The primary motivation is speeding up tests for non-responsive
nameservers. It's also base infrastructure for future work to compute
retry timeouts dynamically.

Using default timeouts (RES_TIMEOUT = 5 seconds):
  ResolverTest.GetAddrInfoV6_nonresponsive (45141 ms)

With base_timeout_msec=100:
  ResolverTest.GetAddrInfoV6_nonresponsive (1264 ms)

Test: executed unsubmitted test from aosp/713993
Change-Id: Id902089ca69ca8d28032180ba51e8937262ef490