Added new iteration to RecoveryWhileUnderLoadTests

We want to check whether the issue causing the test to fail would be fixed by an additional refresh or not
Search action now log in debug what shards/nodes were used before moving to second phase
Added  a debug log for executing a refresh request on a shard.
Previously added logging in TransportRefreshAction caused NPE if search shards had errors (or was not yet started/assigned)
Better formatting for logging in TransportRefreshAction
Add 'min_input_len' to completion suggester

Restrict the size of the input length to a reasonable size otherwise very
long strings can cause StackOverflowExceptions deep down in lucene land.
Yet, this is simply a saftly limit set to `50` UTF-16 codepoints by default.
This limit is only present at index time and not at query time. If prefix
completions > 50 UTF-16 codepoints are expected / desired this limit should be raised.
Critical string sizes are beyone the 1k UTF-16 Codepoints limit.

Closes #3596