[analyzer] Implemented SMT generic API

Summary:
Created new SMT generic API.

Small changes to `Z3ConstraintManager` because of the new generic objects (`SMTSort` and `SMTExpr`) returned by `SMTSolver`.

Reviewers: george.karpenkov, NoQ

Reviewed By: george.karpenkov

Subscribers: mgorny, xazax.hun, szepet, a.sidorin

Differential Revision: https://reviews.llvm.org/D49495

llvm-svn: 337918