Deprecate Material 2 text style properties

[rami-a]

Now that Material 3 text styles have been added to the TextTheme, we can deprecate the Material 2 styles (just like we did for Material 1).

Proposal

• Deprecate (and eventually remove following the official deprecation policy) M2 text styles from TextTheme, for example display1, bodyText2, etc.

[bernaferrari]

Can we make the newer styles not nullable?

[iapicca]

shold this be tracked in
#91605
https://github.com/flutter/flutter/projects/211 ?

[github-actions]

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