[ImplicitNullChecks] Support complex addressing mode

The pass is updated to handle loads through complex addressing mode,
specifically, when we have a scaled register and a scale.
It requires two API updates in TII which have been implemented for X86.

See added IR and MIR testcases.

Tests-Run: make check
Reviewed-By: reames, danstrushin
Differential Revision: https://reviews.llvm.org/D87148