feat: add shared filter to workspaces query (#19807)

Adds a `shared:<boolean>` search query to the `/workspaces [get]`
endpoint


https://github.com/user-attachments/assets/ccf84bd9-c1fd-4085-825b-2e3176a2d488

Closes
[coder/internal#972](https://github.com/coder/internal/issues/972)

coderd/database/queries/workspaces.sql

@@ -378,6 +378,13 @@ WHERE
 			latest_build.has_external_agent = sqlc.narg('has_external_agent') :: boolean
 		ELSE true
 	END
+	-- Filter by shared status
+	AND CASE
+		WHEN sqlc.narg('shared') :: boolean IS NOT NULL THEN
+			(workspaces.user_acl != '{}'::jsonb OR workspaces.group_acl != '{}'::jsonb) = sqlc.narg('shared') :: boolean
+		ELSE true
+	END
+
 	-- Authorize Filter clause will be injected below in GetAuthorizedWorkspaces
 	-- @authorize_filter
 ), filtered_workspaces_order AS (