Rearrange imports in databricks.sdk.runtime to improve local editor…

… experience (#219)

## Changes
<!-- Summary of your changes that are easy to understand -->

The type hinting here means that VSCode does not give useful syntax
highlights / code completions.

This is the current experience on `main`:
<img width="428" alt="image"
src="https://github.com/databricks/databricks-sdk-py/assets/17158624/72d2c3eb-cc3a-4f95-9f09-7d43a8f2815e">
<img width="428" alt="image"
src="https://github.com/databricks/databricks-sdk-py/assets/17158624/34b04de0-5996-4a2e-a0d2-b26a8c9d3da9">

With these changes this becomes:
<img width="428" alt="image"
src="https://github.com/databricks/databricks-sdk-py/assets/17158624/99a91d82-f06a-4883-b131-7f96a82edd80">
<img width="818" alt="image"
src="https://github.com/databricks/databricks-sdk-py/assets/17158624/ce684fd0-f550-4afe-bc46-1187b6dd4b49">
 

## Tests
<!-- 
How is this tested? Please see the checklist below and also describe any
other relevant tests
-->

- [x] `make test` run locally
- [x] `make fmt` applied
- [ ] relevant integration tests applied

databricks/sdk/runtime/__init__.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 is_local_implementation = True
 
 # All objects that are injected into the Notebook's user namespace should also be made
@@ -31,15 +33,22 @@
         _globals[var] = userNamespaceGlobals[var]
     is_local_implementation = False
 except ImportError:
+    from typing import Type, cast
+
     # OSS implementation
     is_local_implementation = True
 
     try:
+        from . import stub
         from .stub import *
+        dbutils_type = Type[stub.dbutils]
     except (ImportError, NameError):
         from databricks.sdk.dbutils import RemoteDbUtils
 
         # this assumes that all environment variables are set
         dbutils = RemoteDbUtils()
+        dbutils_type = RemoteDbUtils
+
+    dbutils = cast(dbutils_type, dbutils)
 
 __all__ = ['dbutils'] if is_local_implementation else dbruntime_objects