[vm] Separate generic mixin class into typed and non-typed to reduce code size

The VM uses copying mixins with support for mixin application deduplication. Due to the
different generic type arguments to the mixin the deduplication did not
apply.

This CL splits up the generic mixin class into two, which makes the
non-typed mixin application classes sharable. This reduces AOT size.

Issue #37345

Change-Id: I200f0785d72e8b37e3320f37da00e0c6de653a38
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/106909
Reviewed-by: Todd Volkert <tvolkert@google.com>
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>

Author: mkustermann