feat(dialog): set default actions alignment with injection token

[json-derulo]

Feature Description

I want the dialog actions to be aligned to the right by default. Currently this is not part of the MatDialogConfig, so it cannot be set via the MAT_DIALOG_DEFAULT_OPTIONS injection token. It can only be achieved by setting the align input for each usage of the mat-dialog-actions component:

<mat-dialog-actions align="end">
</mat-dialog-actions>

My suggestion is to add an optional alignActions property to the MatDialogConfig interface to control the default alignment.

Use Case

The actions alignment should be changeable at a single point for the whole application, so it is easier to maintain in larger code bases.