[MemCpyOptimizer] Preserve analyses and replace use of lambdas to get them.

Summary:
Analyses are preserved in MemCpyOptimizer.
Get analyses before running the pass and store the pointers, instead of
using lambdas and getting them every time on demand.

Reviewers: lenary, deadalnix, mehdi_amini, nikic, efriedma

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74494