update_analyze_test_checks: support output from LAA (#67584)

update_analyze_test_checks.py is an invaluable tool in updating tests.
Unfortunately, it only supports output from the CostModel,
ScalarEvolution, and LoopVectorize analyses. Many LoopAccessAnalysis
tests use hand-crafted CHECK lines, and it is moreover tedious to
generate these CHECK lines, as the output fom the analysis is not
stable, and requires the test-writer to hand-craft FileCheck matches.
Alleviate this pain, and support output from:

  $ opt -passes='print<loop-accesses>'

This patch includes several non-trivial changes including:
- Preserving whitespace at the beginning of the line, so that the LAA
output can be properly indented.
- Regexes matching the unstable output, which is basically a pointer
address hex.
- Separating is_analyze from preserve_names clearly, as the former was
formerly used as an overload for the latter.

To demonstate the utility of this patch, several tests in
LoopAccessAnalysis have been auto-generated by
update_analyze_test_checks.py.