ENH: Implement fastpath for masked indexes in join

[phofl]

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

As of right now, masked indexes go through object even though we only use the join functions when we are monotonic, e.g. no NA present. We can simply use the numpy array to perform the join.

       before           after         ratio
     [026a83e0]       [d804bced]
-     5.82±0.02ms      1.38±0.02ms     0.24  index_object.SetOperations.time_operation('monotonic', 'ea_int', 'intersection')
-     4.08±0.03ms         452±10μs     0.11  index_object.SetOperations.time_operation('monotonic', 'ea_int', 'union')

This is related to #49420, will make it a bit easier to review since it solves the join changes

[mroeschke]

Where is the monoticity of self._values._data checked?

[phofl]

Using those functions is guarded by those checks. The actual join implementations here only work with monotonic data. As soon as we reach _inner_indexer and others we have to be monotonic

[mroeschke]

Ah okay cool

[mroeschke]

Thanks @phofl