[std/hl] move some hl.Format into lib format/heaps

[yuxiaomao]

This PR address the problem that some hl.Format function should not exist in std.
The idea is to split hl.Format functions into 3 types:

• digest: needed by some std crypto function (hl/_std/haxe/crypto), we can keep it
  • It can also be moved into hl.Api if we'd like to remove this file
• png, jpg, dxt, scale: basic image function, will be moved to format.hl.Native
  • [hl] Move hl.Format to format.hl.Native format#112
• Mikktspace, and other heaps-specific functionalities such as MeshOptimizer: will be moved/added to hxd.MeshTools (in heaps)
  • [hl] Move hl.Format into lib format/heaps HeapsIO/heaps#1250

I don't know if it's ok to remove totally these functions so I just declared them deprecated.

[Simn]

I would prefer removing this, there's a roughly 100% chance that you guys were the only ones using it anyway.

[kLabz]

I would prefer removing this, there's a roughly 100% chance that you guys were the only ones using it anyway.

Well, heaps uses some of these so I'm not sure about this 🤔
(it's probably fine either way, especially if heaps is updated quickly)

[yuxiaomao]

If the changes is validated, I'll make sure to merge some heaps PR at the same time.

[Simn]

Consider them validated.