revive: Rework the instruction benchmark (#7721)

Fixes https://github.com/paritytech/polkadot-sdk/issues/6157

This fixes the last remaining benchmark that was not correct since it
was too low level to be written in Rust. Instead, we opted.

This PR changes the benchmark that determines the scaling from
`ref_time` to PolkaVM `Gas` by benchmarking the absolute worst case of
an instruction: One that causes two cache misses by touching two cache
lines.

The Contract itself is designed to be as simple as possible. It does
random unaligned reads in a loop until the `r` (repetition) number is
reached. The randomness is fully generated by the host and written to
the guests memory before the benchmark is run. This allows the benchmark
to determine the influence of one loop iteration via linear regression.

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Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: xermicus <cyrill@parity.io>
Co-authored-by: PG Herveou <pgherveou@gmail.com>