Frozen binnings

[janpipek]

Refactor binning instances to frozen attrs models.

This has a few consequences:

• they cannot change in-place, thus all changes in an adaptive histogram bins is performed as replacing one binning with another one
• instead of "adaptation", we call the operation "coercing" (with two different implementations for values and for another histogram)
• the API of BinningBase is slightly changed
• the semantics of includes_right_edge, align, range, ..., etc. in fixed_width_binning is slightly changed

Some other changes:

• the fixed width as the only adaptable

Testing:

• all tests pass
• all documentation notebooks render reasonably