Metal painter improvements

[crazyjul]

This PR contains lots of improvements for the metal targets :

• Better clearing support (use to required a load and store before clearing)
• Correct support of constant buffers
• Depth buffer + depth state support
• Blend modes
• High DPI

This renderer also works with iOs, I'll submit the iOs support in a follow up

This PR also introduce a macOs script to build the tool and editor, but it requires a change in the deps repo to support arm64

If you approve the way I select the reps for x86_64 and arm64, I'll make a PR in the dept repo and update the submodule here