kvdb+refactor: move all general sqlite code to seprate dir

In this commit, all the sql, non-postgres-specific, code is moved out of
the postgres package and into a new sqlbase package. This will make it
more easily reusable for future sql integrations.

kvdb/sqlbase/no_sql.go

@@ -0,0 +1,5 @@
+//go:build !kvdb_postgres
+
+package sqlbase
+
+func Init(maxConnections int) {}