Initial implementation benchmarks for the rune cli

[saidinesh5]

We use the criterion benchmark framework for this task, as the built in rust benchmarks aren't yet available in rust stable.
Each of the benchmarks use a sample size of 10 instead of the default 100.

These benchmarks measure the time taken for:

1. build - sine rune
2. inference - sine rune, microspeech, style transfer.

The results on my Linux Ryzen 7 1700 machine look like:

TODO: Try to enable Github Actions for these benchmarks These benchmarks can be run manually before each release, so we aren't adding them to github actions for now

[Michael-F-Bryan]

Overall I'm really happy with this PR!

As discussed on Slack we might either choose to ignore build times or only run benchmarks locally before a release. I'm lazy so I'd prefer to just have CI run our benchmarks every time something gets merged into master, but including it as a manual step in our release process might work too. What do you think will be the best way forward?

There are a couple stylistic comments (e.g. functions take PathBuf by value or &Path by reference, but not &PathBuf because then you've got double indirection), but that's something a quick clippy run would point out so I'm not overly concerned.

[Michael-F-Bryan]

If we don't call it then the destructor will make sure our temporary directory is cleaned up so it's up to you whether you want to write an explicit close() here and blow up if it failed or skip an extra line of code.

From their docs:

Although TempDir removes the directory on drop, in the destructor any errors are ignored. To detect errors cleaning up the temporary directory, call close instead.

[Michael-F-Bryan]

This is more personal preference than anything else, but I'd typically write it like this:

Suggested change

	let base = example_dir().join("sine");
	let rune = parse_runefile(base.join("Runefile.yml").as_path()).unwrap();
	let base = example_dir().join("sine");
	let runefile = base.join("Runefile.yml");
	let rune = parse_runefile(&runefile).unwrap();

Or alternatively you could make parse_runefile() accept anything which is impl AsRef<Path>. That would also let us accept string literals if we were using it for other tests.

[f0rodo]

This is a long time coming!!