docs: override prop in manifest

[DavideMininni-Fincons]

As already experienced with generics (see 5702592), the manifest generation has some issue when working with superclasses and mixin.
This time, i noticed that if an element extends a base class, and the base class implements a mixin and overrides some of its property, the overriding is not considered during the manifest generation, because the inheritance chain is traversed from the outer to the inner element and not vice versa as expected.

Eg. all the buttons extend the SbbButtonBaseElement class, which implements the SbbFormAssociatedMixin.
The SbbButtonBaseElement defines via getter/setter the form property by overriding the default form getter from the mixin; however, the override is not reflected in the manifest, which mark the form member as readonly, as does with getters. Also the inheritedFrom prop refers to the mixin and not to the base class.

This behavior is problematic when the Angular classes are generated, so a manual override must be done; I noticed that the corresponding attribute field is not changed when the inheritance chain it traversed, so it can be used as a 'baseline'.
As a consequence, the form jsDoc is overridden in all the button components, taking the correct description from the SbbButtonBaseElement.

NOTE: even if this PR fixes the Angular classes generation, it is not possible to automatically fix the type mismatch between get/set, so this should be done manually in the Angular repo.

  // button-base-element.ts
  
  @property()
  public override set form(value: string) {
    ...
  }
  public override get form(): HTMLFormElement | null {
     ... 
   }

[kyubisation]

Generally LGTM, apart from the issue with the formatting

[jeripeierSBB]

Nice! LGTM