fix(sqlite): avoid rowid on kv table (#10367)

No migration on this as it has no practical impact, just a slight
cleanup for new installations.

Also a refactor of how we declare single column primary keys, for
consistency.

Signed-off-by: Jakob Borg <jakob@kastelo.net>

internal/db/sqlite/sql/schema/common/10-schema.sql

@@ -6,9 +6,8 @@
 
 -- Schema migrations hold the list of historical migrations applied
 CREATE TABLE IF NOT EXISTS schemamigrations (
-    schema_version INTEGER NOT NULL,
+    schema_version INTEGER NOT NULL PRIMARY KEY,
     applied_at INTEGER NOT NULL, -- unix nanos
-    syncthing_version TEXT NOT NULL COLLATE BINARY,
-    PRIMARY KEY(schema_version)
+    syncthing_version TEXT NOT NULL COLLATE BINARY
 ) STRICT
 ;