assert "dr_app_pc_from_cache_pc not supported from the thread exit event" in client.thread_exit_xl8

The test still passes despite this assert:

https://ci.appveyor.com/project/DynamoRIO/dynamorio/builds/24074579
```
[00:08:19] Start 147: code_api|client.thread_exit_xl8
[00:08:19]
[00:08:19] 147: Test command: C:\projects\dynamorio\build\build_debug-internal-32\bin32\drrun.exe "-s" "90" "-quiet" "-debug" "-use_dll" "C:/projects/dynamorio/build/build_debug-internal-32/lib32/debug/dynamorio.dll" "-exit0" "-stderr_mask" "0xC" "-msgbox_mask" "0" "-dumpcore_mask" "0x7d" "-staged" "-code_api" "-c" "C:/projects/dynamorio/build/build_debug-internal-32/suite/tests/bin/client.thread_exit_xl8.dll.dll" "--" "C:/projects/dynamorio/build/build_debug-internal-32/suite/tests/bin/simple_app.exe"
[00:08:19] 147: Test timeout computed to be: 600
[00:08:19] 147: Hello, world!
[00:08:19] 147:
[00:08:19] 147:

Start with the client.thread_exit_xl8 test and reproduce it using the AppVeyor command shown in the report. Inspect how the test records or validates the thread-exit event and the usage error from core/lib/instrument.c; done means the test fails when the unsupported dr_app_pc_from_cache_pc assertion occurs.

Written by the indexing model from the issue text.