[llvm] [AArch64] Provide a custom decoder for LDR_ZA/STR_ZA (PR #156363)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lldb-aarch64-ubuntu` running on `linaro-lldb-aarch64-ubuntu` while building `llvm` at step 6 "test".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/59/builds/23746

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test) failure: build (failure)
...
PASS: lldb-api :: functionalities/breakpoint/breakpoint_locations/after_rebuild/TestLocationsAfterRebuild.py (317 of 2316)
PASS: lldb-api :: driver/terminal/TestTerminalDimensions.py (318 of 2316)
PASS: lldb-api :: driver/quit_speed/TestQuitWithProcess.py (319 of 2316)
PASS: lldb-api :: functionalities/breakpoint/breakpoint_on_overload/TestBreakOnOverload.py (320 of 2316)
PASS: lldb-api :: functionalities/breakpoint/breakpoint_conditions/TestBreakpointConditions.py (321 of 2316)
PASS: lldb-api :: functionalities/breakpoint/breakpoint_names/TestBreakpointNames.py (322 of 2316)
PASS: lldb-api :: functionalities/breakpoint/breakpoint_on_lambda_capture/TestBreakOnLambdaCapture.py (323 of 2316)
PASS: lldb-api :: functionalities/breakpoint/breakpoint_with_realpath_and_source_map/TestBreakpoint.py (324 of 2316)
PASS: lldb-api :: functionalities/breakpoint/breakpoint_options/TestBreakpointOptions.py (325 of 2316)
PASS: lldb-api :: functionalities/breakpoint/breakpoint_reset_upon_run/TestBreakpointResetUponRun.py (326 of 2316)
FAIL: lldb-api :: commands/watchpoints/hello_watchlocation/TestWatchLocation.py (327 of 2316)
******************** TEST 'lldb-api :: commands/watchpoints/hello_watchlocation/TestWatchLocation.py' FAILED ********************
Script:
--
/usr/bin/python3.10 /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/dotest.py -u CXXFLAGS -u CFLAGS --env LLVM_LIBS_DIR=/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./lib --env LLVM_INCLUDE_DIR=/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/include --env LLVM_TOOLS_DIR=/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin --arch aarch64 --build-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lldb-test-build.noindex --lldb-module-cache-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lldb-test-build.noindex/module-cache-lldb/lldb-api --clang-module-cache-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lldb-test-build.noindex/module-cache-clang/lldb-api --executable /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin/lldb --compiler /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin/clang --dsymutil /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin/dsymutil --make /usr/bin/gmake --llvm-tools-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./bin --lldb-obj-root /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/tools/lldb --lldb-libs-dir /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/./lib --cmake-build-type Release /home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/commands/watchpoints/hello_watchlocation -p TestWatchLocation.py
--
Exit Code: 1

Command Output (stdout):
--
lldb version 22.0.0git (https://github.com/llvm/llvm-project.git revision 25498dfef000f906ad4287d09c4e036a27552cb6)
  clang revision 25498dfef000f906ad4287d09c4e036a27552cb6
  llvm revision 25498dfef000f906ad4287d09c4e036a27552cb6
Skipping the following test categories: ['libc++', 'msvcstl', 'dsym', 'gmodules', 'debugserver', 'objc']

--
Command Output (stderr):
--
FAIL: LLDB (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang-aarch64) :: test_hello_watchlocation (TestWatchLocation.HelloWatchLocationTestCase)
======================================================================
FAIL: test_hello_watchlocation (TestWatchLocation.HelloWatchLocationTestCase)
   Test watching a location with '-s size' option.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/test/API/commands/watchpoints/hello_watchlocation/TestWatchLocation.py", line 97, in test_hello_watchlocation
    self.expect(
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/lldbtest.py", line 2440, in expect
    self.runCmd(
  File "/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/lldbtest.py", line 1005, in runCmd
    self.assertTrue(self.res.Succeeded(), msg + output)
AssertionError: False is not true : Process should be stopped due to watchpoint
Error output:
error: process must be launched

Config=aarch64-/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/bin/clang
----------------------------------------------------------------------
Ran 1 test in 10.581s

FAILED (failures=1)

```

</details>

https://github.com/llvm/llvm-project/pull/156363