Extract Classes into separate modules

[Eve-ning]

Refactors to modularize interfaces and classes.

Key changes:

Separation of Interfaces and Typing:

• Moved the IsAligned interface (for rectangles with defined shapes) from ndrect/ndrect.py into its own module, ndrect/_is_aligned.py. [1] [2]
• Moved the IsSequenceable interface (for rectangles that can be sequenced) from ndrect/ndrect.py into a new module, ndrect/_is_sequenceable.py. [1] [2]
• Created a new module ndrect/_typing.py to define standard types such as DimensionName and DimensionLength. [1] [2]

Class Refactoring and Modularization:

• Moved the implementation of NDRectComplexUnaligned from ndrect/ndrect.py into its own file, ndrect/ndrect_complex_unaligned.py. [1] [2]
• Moved the implementation of NDRectComplex (aligned complex rectangles) from ndrect/ndrect.py into its own file, ndrect/ndrect_complex.py. [1] [2]