[BUG] Installation._unmarshal initializes databricks.sdk.core.Config when the value is None

[JCZuurmond]

Description

The following code initiliatizes a databricks.sdk.core.Config when the value inst is None

blueprint/src/databricks/labs/blueprint/installation.py

Lines 626 to 629 in cb1b8f0

	if type_ref == databricks.sdk.core.Config:
	if not inst:
	inst = {}
	return databricks.sdk.core.Config(**inst) # type: ignore[return-value]

This causes a bug in UCX when we load and save the WorkspaceConfig as that data classes has a databricks.sdk.core.Config attribute which is by default None and after loading it became databricks.sdk.core.Config(**{}). This field causes issues when it the config is used by our RuntimeContext which expects a different config than our cli context.

Reproduce

workspace_context: WorkspaceContext  # Created by the Databricks cli
config = workspace_context.installation.load(WorkspaceConfig)
workspace_context.installation.save(config)