Add a schema to extensions, to prevent installing extensions on too old of a Zed version (#9599)

Release Notes:

- N/A

---------

Co-authored-by: Marshall <marshall@zed.dev>

crates/collab/migrations.sqlite/20221109000000_test_schema.sql

@@ -373,6 +373,7 @@ CREATE TABLE extension_versions (
     authors TEXT NOT NULL,
     repository TEXT NOT NULL,
     description TEXT NOT NULL,
+    schema_version INTEGER NOT NULL DEFAULT 0,
     download_count INTEGER NOT NULL DEFAULT 0,
     PRIMARY KEY (extension_id, version)
 );