Introduces @@optimizer_switch flag: hash_join_cardinality

When this option is on, use EITS statistics to produce tighter bounds
for hash join output cardinality.

This patch is an extension / replacement to a similar patch in 10.6

New features:
- optimizer_switch hash_join_cardinality is on by default
- records_out is set to fanout when HASH is used
- Fixed bug in is_eits_usable: The function did not work with views