[CodeGen] Stop storing alignment information into pointers in Address

This reverts b1613f05. The change was
made in an attempt to reduce memory consumption by storing the alignment
information into pointers, but it turns out it doesn't make much
difference.

https://llvm-compile-time-tracker.com/compare.php?from=998ad085e865f2e5acc589d6bee0e3379042da2e&to=5de4a1989c474f37ac03f20ccb0aef50f6e3b854&stat=max-rss

This fixes a bug introduced in https://reviews.llvm.org/D142584. The
patch reduced the number of bits used for alignment from 6 bits to 5
bits, which made it impossible to encode the maximum allowed alignment
in llvm (1 << 32).

Differential Revision: https://reviews.llvm.org/D144686