General: Removed silo references and terminal splash

[iLLiCiTiT]

Brief description

Silo is not used in OpenPype for a long time and still there are references to it in the code. Also there is terminal splash which is not used anymore and can be removed.

Description

All references to silo were removed in the code with few deprecated comments related to it. Removed terminal splash was used at first versions of OpenPype 3 but is not used because of huge amount of lines added to stdout. Also reduced Loader tool logic related to roots which is now simplified so library loader logic does not need LibrarySubsetWidget anymore.

Changes

• removed silo references from code
• removed terminal_splash.py and splash.txt from openpype/lib
• Loader tool is not using registered_root but Anatomy.roots based on current project in context

Testing notes:

1. Both loader and library loader should work when copying source of version
2. Everything else should work as expected (all removed code was not used)

[antirotor]

I will mourn the removal of animated splash even if it wasn't used. R.I.P. ✝️