updated (m)termvectors api specs to reflect #7530 which made it into 1.4
Core: don't block shard stats when phase 3 of recovery is running

Today, shard stats are blocked while phase 3 of recovery (replay xlog)
is running; this change removes the engine readLock from shard stats
so it's not blocked.

Closes #8910
[TEST] Remove random templates for ConcurrentDynamicTemplateTests
Remove circular dependency between IndicesService and IndicesStore