[NO ISSUE][COMP] Extension-specific SET statements

[NO ISSUE][COMP] Extension-specific SET statements

- user model changes: no
- storage format changes: no
- interface changes: no

Adding a method to alter the SET parameter whitelist, so as to allow
extensions to more flexibly use the SET statement.

Change-Id: Ib6bafec178b959025e8822925eb27cd41d8bef03
Reviewed-on: https://asterix-gerrit.ics.uci.edu/c/asterixdb/+/15283
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Ian Maxon <imaxon@uci.edu>