[TECH DEBT] Add type hints for cached properties (#2813)

## Changes
Add type hints for cached properties and resolve the linting issues
found after adding the type hints. Would have caught the integration
test issues introduced in #2772

---------

Co-authored-by: Serge Smertin <serge.smertin@databricks.com>

src/databricks/labs/ucx/account/aggregate.py

@@ -49,7 +49,7 @@ def __init__(
         self._workspace_context_factory = workspace_context_factory
 
     @cached_property
-    def _workspace_contexts(self):
+    def _workspace_contexts(self) -> list[WorkspaceContext]:
         contexts = []
         for workspace_client in self._account_workspaces.workspace_clients():
             ctx = self._workspace_context_factory(workspace_client)

src/databricks/labs/ucx/cli.py

@@ -593,11 +593,19 @@ def assign_metastore(
     ctx: AccountContext | None = None,
 ):
     """Assign metastore to a workspace"""
+    if workspace_id is None:
+        logger.error("--workspace-id is a required parameter.")
+        return
+    try:
+        workspace_id_casted = int(workspace_id)
+    except ValueError:
+        logger.error("--workspace-id should be an integer.")
+        return
     logger.info(f"Account ID: {a.config.account_id}")
     ctx = ctx or AccountContext(a)
     ctx.account_metastores.assign_metastore(
         ctx.prompts,
-        workspace_id,
+        workspace_id_casted,
         metastore_id=metastore_id,
         default_catalog=default_catalog,
     )
@@ -635,7 +643,7 @@ def migrate_tables(
         deployed_workflows = workspace_context.deployed_workflows
         deployed_workflows.run_workflow("migrate-tables")
 
-        tables = workspace_context.tables_crawler.snapshot()
+        tables = list(workspace_context.tables_crawler.snapshot())
         hiveserde_tables = [table for table in tables if table.what == What.EXTERNAL_HIVESERDE]
         if len(hiveserde_tables) > 0:
             percentage_hiveserde_tables = len(hiveserde_tables) / len(tables) * 100

src/databricks/labs/ucx/contexts/account_cli.py

@@ -19,21 +19,21 @@ def account_client(self) -> AccountClient:
         return self._ac
 
     @cached_property
-    def workspace_ids(self):
+    def workspace_ids(self) -> list[int]:
         return [int(_.strip()) for _ in self.named_parameters.get("workspace_ids", "").split(",") if _]
 
     @cached_property
-    def account_workspaces(self):
+    def account_workspaces(self) -> AccountWorkspaces:
         return AccountWorkspaces(self.account_client, self.workspace_ids)
 
     @cached_property
-    def account_aggregate(self):
+    def account_aggregate(self) -> AccountAggregate:
         return AccountAggregate(self.account_workspaces)
 
     @cached_property
-    def is_account_install(self):
+    def is_account_install(self) -> bool:
         return environ.get("UCX_FORCE_INSTALL") == "account"
 
     @cached_property
-    def account_metastores(self):
+    def account_metastores(self) -> AccountMetastores:
         return AccountMetastores(self.account_client)