Revert "[analyzer] Deprecate `-analyzer-store region` flag"

This reverts commit d50d9946.
Broke check-clang, see comments on https://reviews.llvm.org/D126067

Also revert dependent change "[analyzer] Deprecate the unused 'analyzer-opt-analyze-nested-blocks' cc1 flag"
This reverts commit 07b4a6d0.

Also revert "[analyzer] Fix buildbots after introducing a new frontend warning"
This reverts commit 90374df1.
(See https://reviews.llvm.org/rG90374df15ddc58d823ca42326a76f58e748f20eb)