Implement FK/PK "rely novalidate" constraints for better CBO

Oracle has "RELY NOVALIDATE" option for constraints.. Could be easier for Hive to start with something like that for PK/FK constraints. So CBO has more information for optimizations. It does not have to actually check if that constraint is relationship is true; it can just "rely" on that constraint.

RELY clause:
https://docs.oracle.com/database/121/SQLRF/clauses002.htm#SQLRF52223

"Overview of Constraint States":
https://docs.oracle.com/database/121/DWHSG/schemas.htm#DWHSG9053

• Enforcement
• Validation
• Belief

So FK/PK with "rely novalidate" will have Enforcement&Validate disabled but Belief = RELY as it is possible to do in Oracle and now in Hive (HIVE-13076).

It opens a lot of ways to do additional ways to optimize execution plans.
As explained in Tom Kyte's "Metadata matters"
http://www.peoug.org/wp-content/uploads/2009/12/MetadataMatters_PEOUG_Day2009_TKyte.pdf
pp.30 - "Tell us how the tables relate and we can remove them from the plan...".
pp.35 - "Tell us how the tables relate and we have more access paths available...".