sanity checks: print test failures for analysis even better

Due to parallel work, we both implemented this functionality at the
same time. Switch to my implementation, which has the following
advantages:

- Use some fancy github output labeling to print the entire testlog,
  which causes it to be a collapsible element in the github UI.

- Use --print-errorlogs, which causes the stderr of failing tests (and
  only that) to be printed by default, something that ninja test already
  does ;) because it is smart. Sometimes the failures are obvious from
  there, although not always -- in the case of libuv which prompted
  this, the error output is part of the TAP stream on stdout, and
  errorlogs are only printed based on stderr.

tools/sanity_checks.py

@@ -239,14 +239,18 @@ def check_new_release(self, name: str, builddir: str = '_build'):
             subprocess.check_call(['meson', 'setup', builddir] + options)
         except subprocess.CalledProcessError:
             log_file = Path(builddir, 'meson-logs', 'meson-log.txt')
-            print('\n\n==== meson-logs.txt ====\n', log_file.read_text(encoding='utf-8'))
+            print('::group::==== meson-log.txt ====')
+            print(log_file.read_text(encoding='utf-8'))
+            print('::endgroup::')
             raise
         subprocess.check_call(['meson', 'compile', '-C', builddir])
         try:
-            subprocess.check_call(['meson', 'test', '-C', builddir])
+            subprocess.check_call(['meson', 'test', '-C', builddir, '--print-errorlogs'])
         except subprocess.CalledProcessError:
             log_file = Path(builddir, 'meson-logs', 'testlog.txt')
-            print('\n\n==== testlog.txt ====\n', log_file.read_text(encoding='utf-8'))
+            print('::group::==== testlog.txt ====')
+            print(log_file.read_text(encoding='utf-8'))
+            print('::endgroup::')
             raise
 
     def is_permitted_file(self, subproject: str, filename: str):