[FunC] Enrich testing framework, add code hash checking

@code_hash to match (boc) hash of compiled.fif against expected.
While being much less flexible than @fif_codegen, it nevertheless
gives a guarantee of bytecode stability on compiler modifications.

crypto/func/auto-tests/tests/w6.fc

@@ -14,4 +14,6 @@ int main(int x) {
 {-
     method_id | in | out
 TESTCASE | 0  | 0  | 1
+
+@code_hash 36599880583276393028571473830850694081778552118303309411432666239740650614479
 -}