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/folder/50-mtimes.sql

@@ -6,9 +6,8 @@
 
 --- Backing for the MtimeFS
 CREATE TABLE IF NOT EXISTS mtimes (
-    name TEXT NOT NULL,
+    name TEXT NOT NULL PRIMARY KEY,
     ondisk INTEGER NOT NULL, -- unix nanos
-    virtual INTEGER NOT NULL, -- unix nanos
-    PRIMARY KEY(name)
+    virtual INTEGER NOT NULL -- unix nanos
 ) STRICT, WITHOUT ROWID
 ;