Perf Benchmark

[suvamM]

This PR adds a test which does the following:

1. Generate 1M random test keys using the common annotated security key generator.
2. For each test key, run the high performance identifiable scanning---timing the scan and result extraction.
3. For each result, perform checksum validation---timing the validation.

Then print the mean scan and validation times. This allows us to measure the overhead of performing checksum validation.

[suvamM]

This looks like a bespoke benchmark instead of an idiomatic Rust Benchmark using built-in cargo bench: https://doc.rust-lang.org/1.4.0/book/benchmark-tests.html

Please update to use cargo's benchmarking tool or abandon the PR.

@rwoll This does not look like a stable feature of the Rust toolchain currently. From the link you shared:

Note the test feature gate, which enables this unstable feature.

This benchmark is important to have checked in. So I'll track the bench verb (thanks for the pointer!), and will move it when it becomes stable.