shard not found for non-fastpath queries during concurrent create_distributed_table_concurrently execution

[aykut-bozkurt]

Problem: Shards in non-fast-path insert queries may be invalid because they are deleted by a concurrent create_distributed_table_concurrently. Example case:

session1:
select create_distributed_table_concurrently('xx','id');

session2:
insert into xx select random();
ERROR: could not find valid entry for shard xxx

Expected Solution: We should reroute invalid shards for those queries to prevent unpleasant error logs and execute the query if possible.

[onderkalaci]

Related to #6280