Add mechanism to only include specific txs in a benchmark

[alexghr]

We need a way to benchmark specific txs in order to control how much processing time and data they require.

In #5414 we've added benchmarks for tx size but to be accurate they require very specific txs otherwise the data from other benchmarks or even the test setup could lead to comparing apples and oranges.

I think the ideal case would be to "tag" test transactions in a specific way, e.g.:

await testContract.methods.transfer(alice, bob, 1n, 0).send({
  metricsTag: "tx_size_comparison"
}).wait()

And the metrics logs to pick up these tags when they're captured