Fix DVE-1592.
+ Rearrange column modifier parsing slightly to handle inline key defs:
  - 'PRIMARY KEY'
  - 'UNIQUE KEY'
  - 'UNIQUE'
  - 'KEY'
+ In transutils clean up the case where we may have UNIQUE, KEY.

Also, make sure that we clear any parsing related values at the appropriate time,
specifically, lose the reference to the input sql.
PE-1591, PE-1593 - Re-enabled mirror tests.
Arrange to clear the orig sql off of the schema context as soon as the parse is finished.