Add a missing valid triple "aarch64-apple-macosx" for usability.

As with the other update scripts this takes the output of
-passes=print<gisel-value-tracking> and inserts the results into an
existing mir file. This means that the input is a lot like
update_analysis_test_checks.py, and the output needs to insert into a
mir file similarly to update_mir_test_checks.py. The code used to do the
inserting has been moved to common, to allow it to be reused. Otherwise
it tries to reuse the existing infrastructure, and
update_givaluetracking_test_checks is kept relatively short.

UpdateTestChecks has a make_analyzer_generalizer to replace pointer
addressess from the debug output of LAA with a pattern, which is an
acceptable solution when there is one RUN line. However, when there are
multiple RUN lines with a common pattern, UTC fails to recognize common
output due to mismatched pointer addresses. Instead of hacking UTC scrub
the output before comparing the outputs from the different RUN lines,
fix the issue once and for all by making LAA not output unstable pointer
addresses in the first place.

The removal of the now-dead make_analyzer_generalizer is left as a
non-trivial exercise for a follow-up.

The .syntax unified directive and .codeX/.code X directives are, other
than some simple common printing code, exclusively implemented in the
targets themselves. Thus, remove the corresponding MCAF_* flags and
reimplement the directives solely within the targets. This avoids
exposing all targets to all other targets' flags.

Since MCAF_SubsectionsViaSymbols is all that remains, convert it to its
own function like other directives, simplifying its implementation.

Note that, on X86, we now always need a target streamer when parsing
assembly, as it's now used for directives that aren't COFF-specific. It
still does not however need to do anything when producing a non-COFF
object file, so this commit does not introduce any new target streamers.

There is some churn in test output, and corresponding UTC regex changes,
due to comments no longer being flushed by these various directives (and
EmitEOL is not exposed outside MCAsmStreamer.cpp so we couldn't do so
even if we wanted to), but that was a bit odd to be doing anyway.

This is motivated by Morello LLVM, which adds yet another assembler flag
to distinguish A64 and C64 instruction sets, but did not update every
switch and so emits warnings during the build. Rather than fix those
warnings it seems better to instead make the problem not exist in the
first place via this change.

LLVM prints debug records like `#dbg_value` indented 2 additional spaces.

Avoid baking in absolute paths in check lines generated for DIFile
metadata. Generated test checks cannot be sensitive to absolute paths
anyway, as those vary with the environment, but there could be
situations where some sensitivity to partial paths is required for
certain tests. This implementation just assumes such tests aren't worth
the effort to support, but it could be supported in the future.

This is most useful for update_cc_test_checks with debug info enabled,
where the test writer cannot manipulate the paths within the generated
IR directly.

Whilst trying to clean up some loop vectoriser IR tests (see
test/Transforms/LoopVectorize/AArch64/partial-reduce-chained.ll
for example) a reviewer on PR #129047 suggested it would be
nice to have an option to stop generating CHECK lines after a
certain point. Typically when performing a transformation with
the loop vectoriser we don't usually care about any CHECK lines
generated for the scalar tail of the loop, since the scalar
loop is kept intact. Previously if you wanted to eliminate such
unwanted CHECK lines you had to run the update script, then
manually delete all the lines corresponding to the scalar loop.
This can be very time consuming if the tests ever need changing.

What I've tried to do here is add a new --filter-out-after
option alongside the existing --filter* options that provides
support for stopping the generation of any CHECK lines beyond
the line that matches the filter. With the existing filter
options we never generate CHECK-NEXT lines, but we still care
about ordering with --filter-out-after so I've amended the
code to ensure we treat this filter differently.

When --check-globals none, we skipped all the globals in check lines.
However, we are still checking the meta info in function defintion.

The generated checks are still sensitive to metadata changes.

This is to scrub the meta info and match them with {{.*}} instead.

Modify the DA pretty printer to match the output of other analysis
passes. This enables update_analyze_test_checks.py to also work on DA
tests. Auto generate all the Dependence Analysis tests.

For some ABIs `update_cc_test_checks.py` is unable to generate tests
because of the mismatch between the mangled function names reported by
clang's `-asd-dump` and the function names in LLVM IR.

This patch fixes it by striping the leading underscore from the mangled
name for global functions if the data layout string says they have one.