DBZ-860 DBZ-869 DBZ-870 Default value handling fixes

[jpechane]

This is the issue I was talking about yesterday. This PR fixes 3 problems

1. Default value parsing was not tested with antlr parser
2. Antlr parser was not handling listeners list as a stack for ALTER TABLE. We should probably audit the rest of the code for similar problems.
3. 0 is a valid value for dat/time default values

[gunnarmorling]

Hey @jpechane, I've added one commit for testing 0 being a valid default value for DATE columns. Interestingly, this one fails when run with the legacy parser. I've therefore added it to the Antlr-based test only, the idea being that we'd focusing on the Antlr parser for any fixes going forward. I'd make exceptions for high-profile issues, but given that the non-strict mode should be not common and using 0 as a default even less so, I felt it's acceptable to keep the fix limited to Antlr only. WDYT?

[gunnarmorling]

Rebased and applied. Thanks, @jpechane!