Added MeshOptimizer interface in hl.Format

[TothBenoit]

Added MeshOptimizer interface un hl.Format that which can performs various optimization on index and vertex buffers.

[Simn]

Huh, I've never noticed hl.Format before... this doesn't look like something that should be in the Haxe standard library. :/

[yuxiaomao]

We can technically move it into hashlink (except hl.Format.digest used by crypto I think?), just as what was done for DirectX / SDL. But it would needs to fix heaps a little bit.

[kLabz]

except hl.Format.digest used by crypto I think?

We also want to move the crypto package to https://github.com/HaxeFoundation/crypto, but I'm not sure what the best place for hl.Format.digest would be 🤔

[ncannasse]

I agree this is outside the scope of the standard library.
Format started as support for inflate/md5/sha1 and has evolved into jpg/png/dxt and now a bit more.
I will discuss internally but we need to take backward compatibility into account.