[lldb][test] Remove benchmark API tests (#108629)

These benchmarks don't get run as part of the regular API test-suite.
And I'm not aware of any CI running this. Also, I haven't quite managed
to actually run them locally using the `bench.py` script. It looks like
these are obsolete, so I'm proposing to remove the infrastructure around
it entirely.

If anyone does know of a use for these do let me know.

Author: Michael137

lldb/packages/Python/lldbsuite/test/bench.py

@@ -426,18 +426,6 @@ def impl(func):
     return impl
 
 
-def benchmarks_test(func):
-    """Decorate the item as a benchmarks test."""
-
-    def should_skip_benchmarks_test():
-        return "benchmarks test"
-
-    # Mark this function as such to separate them from the regular tests.
-    result = skipTestIfFn(should_skip_benchmarks_test)(func)
-    result.__benchmarks_test__ = True
-    return result
-
-
 def no_debug_info_test(func):
     """Decorate the item as a test what don't use any debug info. If this annotation is specified
     then the test runner won't generate a separate test for each debug info format."""