The new UPGRADING.md file contains a number of items saying that methods have been deprecated but doesn't say what class they apply to. There are at least three of these:

• The following methods have been deprecated, existing usage should switch to secure \core\encryption library:

• • rc4encrypt
  • rc4decrypt
  • endecrypt
    For more information see MDL-81940

• The following method has been deprecated and should not be used any longer: print_grade_menu.

For more information see MDL-82157

• The following files and their contents have been deprecated:

• • lib/soaplib.php
  • lib/tokeniserlib.php
    For more information see MDL-82191

• The following methods have been formally deprecated:

• • get_core_subsystems
  • get_plugin_types
  • get_plugin_list