[analyzer] Cleanup constructors in the Z3 backend

Summary: Left only the constructors that are actually required, and marked the move constructors as deleted. They are not used anymore and we were never sure they've actually worked correctly.

Reviewers: george.karpenkov, NoQ

Reviewed By: george.karpenkov

Subscribers: xazax.hun, baloghadamsoftware, szepet, a.sidorin, Szelethus, donat.nagy, dkrupp

Differential Revision: https://reviews.llvm.org/D54974

llvm-svn: 347777