mathlib

81120aec - refactor(number_theory): reorganize number field results into new subfolder (#16764)

refactor(number_theory): reorganize number field results into new subfolder (#16764) - Create a new dir `number_field` in `number_theory` - Move the current file `number_field.lean` to `number_theory/number_field/basic.lean` - Move the results about embeddings from this file to a new file `number_theory/number_field/embeddings.lean` - Move the file `number_theory/class_number/number_field.lean` to `number_theory/number_field/class_number.lean`