Add `noexcept` declarations for Cython 3.0

[benfred]

This fixes a large performance regression with many of the CPU models.

For instance when training the ml100k dataset, when compiled with Cython 3.0.0:

• Without this change

  DEBUG:implicit:trained model 'bpr' in 69.49404716491699
  DEBUG:implicit:trained model 'lmf' in 42.24160981178284
  DEBUG:implicit:trained model 'als' in 120.11413407325745

• With this change

  DEBUG:implicit:trained model 'bpr' in 0.18895816802978516
  DEBUG:implicit:trained model 'lmf' in 0.06523633003234863
  DEBUG:implicit:trained model 'als' in 1.8809657096862793

Fixes #678