Fix tools helper and allow GST to parse new eest devnet-6 test vectors

[jangko]

The new eest of devnet-6 test vector contains multiple sub fixtures in one json file. The old format(Frontier-Cancun), only contains one sub fixture.

[advaita-saha]

nimbus-eth1/tests/test_generalstate_json.nim

Lines 228 to 229 in 97b17f8

	let folder = if config.legacy: legacyFolder else: newFolder
	let path = "tests" / "fixtures" / folder

It would be better if we can pass single test vector files in debug mode, not from a fixed folder path

[jangko]

Maybe you can try tools/evmstate. It has better defined/standardized cli and consume the same fixtures as gst. It also has better features. I will not make gst better, if it can correctly run test, it already fullfill it's purpose.
evmstate tool is designed as debugging tool from beginning.