fix: concise uuidToBytes

[broofa]

Putting up two possible implementations of uuidToBytes for us to consider:

• This PR, uuidToBytes_concise, is similar to what's on master. Slightly better perf and compactness, pretty readable.
• PR Version 9 improvements #464, uuidToBytes_fast is @awwit's approach in v9, but with the numberToBytes stuff done inline. Yields slightly better performance and saves a few bytes when minified. Not great readability (as tends to be the case with highly optimized code), hence the extra comments.

Here are the numbers for the various flavors:

branch	performance (ops/sec)	size (minified+gzip bytes)1
master2	138-141K	132
v9	209-221K	247
uuidToBytes_concise	146-170K	125
uuidToBytes_fast	228-230K	183

Thoughts? Pick one, I guess. :-)

1. "size" is for just the uuidToBytes() implementation run through jsmin | gzip -c | wc -c
2. master implementation does not currently validate() like the other approaches mentioned here do.

[ctavan]

Tough call, I have no strong opinion 🤷‍♂️

I'm a huge fan of conciseness but I also think bundlesize is not an issue for v3/5 and performance is a promise that this library gives.

I would make good-enough test coverage the requirement for the complex fast solution (I haven't checked how good the test coverage is for this specific code path).

In the next step we could also consider exposing this method alongside bytesToUUID (#180).

[wesleytodd]

TBQH, the code in here is not entirely illegible, especially with the comments. If that is the only concern I would go with it for the small perf and size improvement.

And also, 👍 to exposing it or moving it out to a separate package. Either one would have solved the issue I had in #180

[broofa]

Moving forward with #464