perf: use LATERAL instead of CTE for json body

* add pgbench test for INSERT and RPC
* use LATERAL for RPC and INSERT
* add tests for inlining

test/pgbench/fixtures.sql

@@ -0,0 +1,7 @@
+\ir ../spec/fixtures/load.sql
+
+ALTER TABLE test.complex_items
+    DROP CONSTRAINT complex_items_pkey;
+
+ALTER TABLE test.complex_items
+    ALTER COLUMN "field-with_sep" DROP NOT NULL;