[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/unbalanced_ret_nested.fc

@@ -32,4 +32,6 @@ TESTCASE | 0 | -5 -4 | 111 -70
 TESTCASE | 0 | -4  3 | -7 40
 TESTCASE | 0 | -4 -5 | -7 1110
 TESTCASE | 0 | -4 -4 | -7 -70
+
+@code_hash 68625253347714662162648433047986779710161195298061582217368558479961252943991
 -}