Remove unused asv directives and verify in the CI that we are not using them
Some of the directives being used in our benchmarks (`asv_bench/benchmarks/`) are deprecated in asv. e.g. in `algorithms.py` each of the benchmark classes defines `goal_time` (e.g. https://github.com/pandas-dev/pandas/blob/master/asv_bench/benchmarks/algorithms.py#L18), but it looks like asv just ignores that: https://asv.readthedocs.io/en/stable/benchmarks.html#benchmark-attributes

We should update the benchmarks to not include unused asv directives, and we should add to `./ci/code_checks.py` a way to identify if unused ones are being used (ideally getting the list of expected directives from `asv` itself).

Originally from https://github.com/pandas-dev/pandas/issues/22884#issuecomment-425657882

@jbrockmendel can you review the issue description and edit if needed please