Expose new Bayer 2/4/16 dither modes in material inspector

[mvaligursky]

When engine 2.22 is out.

The engine's Opacity Dither / Opacity Shadow Dither options are hardcoded in the material inspector at src/editor/inspector/assets/material.ts (Opacity Dither field ~line 552, Opacity Shadow Dither field ~line 575):

```ts
options: [
{ v: 'none', t: 'None' },
{ v: 'bayer8', t: 'Bayer 8' },
{ v: 'bluenoise', t: 'Blue Noise' }
]
```

playcanvas/engine#9117 adds DITHER_BAYER2, DITHER_BAYER4 and DITHER_BAYER16 alongside the existing DITHER_BAYER8. Please add these to both dropdowns' options arrays once that PR lands in an engine release:

```ts
{ v: 'bayer2', t: 'Bayer 2' },
{ v: 'bayer4', t: 'Bayer 4' },
{ v: 'bayer8', t: 'Bayer 8' },
{ v: 'bayer16', t: 'Bayer 16' },
{ v: 'bluenoise', t: 'Blue Noise' }
```

Note: DITHER_IGNNOISE (ignnoise) is also already missing from both dropdowns and could be added at the same time.

Blocked on the engine PR merging and an engine release picking it up.