Introduces a new migration schematic that follows the given
migration plan: https://hackmd.io/@alx/S1XKqMZeS.
First case: The schematic detects decorated directives which
inherit a constructor. The migration ensures that all base
classes until the class with the explicit constructor are
properly decorated with "@Directive()" or "@Component". In
case one of these classes is not decorated, the schematic
adds the abstract "@Directive()" decorator automatically.
Second case: The schematic detects undecorated declarations
and copies the inherited "@Directive()", "@Component" or
"@Pipe" decorator to the undecorated derived class. This
involves non-trivial import rewriting, identifier aliasing
and AOT metadata serializing
(as decorators are not always part of source files)
PR Close#31650
Paul Gschwendtner