M3 prebuilt themes

[crisbeto]

Includes the following changes:

fix(material-experimental/theming): avoid re-emitting the same tokens from the backwards-compatibility styles

Currently the color variant backwards-compatibility styles emit all tokens, even though they were likely emitted already by the theme. This ends up increasing the theme size by about 50kb.

These changes add a emit-overrides-only parameter to the token utilities and use it to only emit the palette-specific styles from the backwards-compatibility mixin.

feat(material/core): add prebuilt themes based on M3

Adds four new prebuilt themes that are using Material Design 3.

[mmalerba]

At some point I think we'll want to deprecate the color="..." API on the components, and at that point we might want to introduce a simpler class-based API to the predefined themes. I'm imagining something like:

<div class="mat-predefined-secondary">
  All components in here are secondary color
  <mat-checkbox />
  <mat-radio />
</div>

The mat-predefined-secondary would be a class you could add to any element to cause all child components to get secondary coloring. For now I think just including the back-compat styles is fine, but we'll want to revisit this later.

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