Tests for highlighting and search operator fixes.

Make sure html is stripped from headings.
Make sure the right headings are returned.
Make sure the search operator is correct.

Bug: 53955
Change-Id: Ide2699f8902d62c609b210e0d1b579fe507a3175
Default to two replicas per shard.

This makes us more resilient to outages and gives us more confidence
when performing a rolling restart because two copies will still be up at
all times.

Change-Id: I13d589945c05a7b2813793acd18beea78df209a2
Merge "Tests for highlighting and search operator fixes."
Merge "Default to two replicas per shard."