v0.0.0-5257-g2f9accc18

Update priority select's codegen.

1) Always use the `unique` modifier when using SystemVerilog.
2) Instead of putting the value for selector==0 in the `default` case arm, make an explicit case arm for 0.
3) Make the default case arm propagate X.
4) Use wildcards with one-hot selectors and rely on `unique` to flag an error if the selector is not one-hot.

PiperOrigin-RevId: 643487953