Deprecate Indigo packages to simplify the architecture.

[HammadYousaf01]

We are currently maintaining custom Indigo packages (header, footer, brand-openedx) instead of using the default Open edX packages. While this allows us to support certain customizations, it introduces several challenges:

• We are responsible for keeping these packages up to date with upstream changes.
• Any further customization requires duplicating and maintaining these packages separately.

We should explore deprecating these Indigo packages to use the standard Open edX packages.

As an alternative, we can try to apply our desired customizations via plugin slots using tutor-indigo. This approach would greatly simplify the overall architecture of the plugin and reduce the need for maintaining separate packages.

[regisb]

FYI copying the openedx brand package is exactly what the authors of tutor-contrib-branding are doing: https://github.com/aulasneo/tutor-contrib-branding/blob/master/tutorbranding/patches/mfe-dockerfile-pre-npm-install 👀 @angonz