chore(fill): decide on an "opcode count" `t8n` interface

[danceratopz]

Motivation: To sanity check tests are executing as intended, in particular benchmark tests. More background here:

• benchmarks: known refactorings and further iteration ideas execution-specs#1554

One way to verify correct test execution would be to verify in the test framework that the intended opcode count was indeed triggered in the EVM. evmone already has an internal "histogram" feature that does exactly this; we need only enable the interface on the t8n tool.

Here's a proposal for that interface:

Flag, Output and Behavior

--opcode.freq=freq.json

Existing flags can be found here:

execution-spec-tests/src/ethereum_clis/transition_tool.py

Lines 210 to 235 in a15263e

	args = [
	str(self.binary),
	"--state.fork",
	t8n_data.fork_name,
	"--input.alloc",
	input_paths["alloc"],
	"--input.env",
	input_paths["env"],
	"--input.txs",
	input_paths["txs"],
	"--output.basedir",
	temp_dir.name,
	"--output.result",
	output_paths["result"],
	"--output.alloc",
	output_paths["alloc"],
	"--output.body",
	output_paths["body"],
	"--state.reward",
	str(t8n_data.reward),
	"--state.chainid",
	str(t8n_data.chain_id),
	]
	if self.trace:
	args.append("--trace")

Contents of freq.json

{
  "MSTORE": 1,
  "PUSH1": 4,
  "RETURN": 1
}

If an opcode is omitted, its frequency is zero.

[danceratopz]

Thanks for the feedback @marioevz & @spencer-tb!

Issue created:

• feat: add an interface to t8n for the histogram opcode counter tracer ipsilon/evmone#1256

I'll leave this issue open for now, just to track, until we have a follow-up issue to use the new t8n functionality.

cc @LouisTsai-Csie