Similar renaming for Font::loadFromMemory and Font::loadFromStream.
The goal is to better express the need to keep the source available,
similar to Music::openFromFile for example.
This new API is built on top of std::variant. This allows us to
store many different event types in a space-efficient way and access
the active event type in a type-safe manner that eliminates the
categories of UB that are possible with unions.
Co-authored-by: kimci86 <kimci86@hotmail.fr>