Augment `BenchmarkTestFiller` with opcode under test and its expected count

[danceratopz]

Currently, the test framework doesn't know which opcode is under test or the expected number of opcode evaluations the test should perform. For example:

execution-specs/tests/benchmark/compute/instruction/test_arithmetic.py

Lines 151 to 158 in 85c6fff

	benchmark_test(
	code_generator=JumpLoopGenerator(
	setup=setup,
	attack_block=attack_block,
	cleanup=cleanup,
	tx_kwargs={"data": tx_data},
	),
	)

If we gave this information to the test spec, BenchmarkTestFiller, e.g., for the case of a "fixed opcode count" test (see #1834):

    benchmark_test(
        opcode_under_test=opcode,  # in test_arithmetic.py, this is a test parameter
        # after #1834 `opcode_count` is a test parameter; could be None for worst case tests (skip check or 
        # test framework specifies it automatically based on gaslimit.
        expected_opcode_count=opcode_count,
        code_generator=JumpLoopGenerator(
            setup=setup,
            attack_block=attack_block,
            cleanup=cleanup,
            tx_kwargs={"data": tx_data},
        ),
    )

then we could leverage evmone's --opcode.count bookkeeping functionality to verify the opcode evaluations during fill.