installation very slow on Windows

[zkat]

For some reason, installation is very very slow on Windows, even compared to other package managers--orogene will often be slower than NPM, not to mention pnpm, which is about twice as fast.

This is even true when using DevDrive and reflinks instead of full file copies. Something weird is going on here and I don't know what.

Fixing this probably entails getting dtrace working on Windows and generating flamegraphs to see what's taking up all that time...

[zkat]

Looking into what nodejs is doing, it looks like there's some mmap happening for the writes. I can see that speeding up things on Windows!

[zkat]

Next up: Probably should make a change to cacache so that it can optionally directly write to a destination file without the temp file step. Roughly 31% of install time is spent just persisting tempfiles (including creating the various directories). This would, of course, make cacache slightly less atomic/concurrency resistant, but if we do #178, this would might be something we don't have to worry about, in the end. That said, it kinda sucks to have to potentially give up that atomicity.

[zkat]

I've created #303 to open up the door to happy path optimizations.