Improve CarDecoder.DecodeCar(byte[]) performance

[alnkesq]

Reading a 3.71 MB CAR file (including ATObject parsing), 10x times, net9.0 Release

Original implementation
01:20.61

This PR
00:02.43

[drasticactions]

What repo are you reading? I've been unable to replicate that benchmark against my repo nor any of my bots I have (With the code as it existed).

That said, the code is fine and I'm using span elsewhere, this should match it.

e. Not saying the original was good, just that it took minutes, not hours.

[alnkesq]

Those are dots, not colons.
It's 1 minute vs 2 seconds, not 1 hour vs 2 minutes.

[drasticactions]

I understood that, but it's a lot! lol. Strike that, I did think hours, it was early, what I can I say.

For my repos it was always within seconds, but the CAR files I've used are all less than a megabyte (Mine is 512 kb). If you can share which repo you used that's that big, I can write tests for it to make sure it doesn't regress in the future.

e. Never mind. Turns out downloading any of the top posters repo will get you much larger repos than I have seen. Yeah, I got plenty to work with now.