Update WorkspacePath to support Python 3.12 (#122)

This PR relates to #120 and updates the `WorkspacePath` implementation
so that it also works under Python 3.12, in addition to Python 3.10 and
Python 3.11.

Changes include:

- Replacing most of the internal implementation to ensure that the
superclass implementations aren't used unless we know they're safe.
(They rely on implementations that changed dramatically between 3.11 and
3.12 and are incompatible with each other.)
 - Additional tests to ensure that the public interfaces are tested.

pyproject.toml

@@ -12,6 +12,7 @@ classifiers = [
     "Programming Language :: Python",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: Implementation :: CPython",
 ]
 dependencies = ["databricks-sdk>=0.16.0"]