PHOENIX-7383 Unify in-memory representation of Conditional TTL expressions and Literal TTL values

[tkhurana]

This PR lays the framework of Conditional TTL.

1. Introduces a new abstract class to hold both conditional TTL and literal TTL values in PTable
2. Simplifies the TTLTracker interface in PhoenixCompactionScanner
3. Introduces the hooks in PhoenixCompactionScanner to work with any type of TTL expression
4. Basic DDL checks in Create/Alter table for Conditional TTL

Tests ran locally: ViewTTLIT, TTLAsPhoenixTTLIT, TableTTLIT