[REF] Change interfaces using tapeId to reference of tape

[TimSiebert1]

This PR changes the methods that rely on tapeId to select a tape from a global buffer to use a reference to the tape directly. The tape_interface methods are adapted accordingly and the global tapeBuffer is removed.

As proposed and discussed with @osander1

• Adapt the docstrings
• Adapt latex docs

[osander1]

That's pretty radical. It was thinking that this change can be made in a backward-compatible way:

• Keep the old methods, let them look for the tape by id, and then forward to the new methods.
• Operator overloading should allow to have the old and new interfaces side-by-side.
• In the constructor of ValueTape, create an id by hashing the pointer value
• Eventually, deprecate the old interface using [[deprecated]]

Also, I am not convinced that suffixing everything with Ptr makes the code more readable. But that's a matter of taste.