[tfds] Rename tfds.core.builder_from_directory -> tfds.builder_from_directory
[tfds] Rename tfds.core.builder_from_directory -> tfds.builder_from_directory

The previous alias is deprecated. The new alias makes it explicit this is part of the user-facing API and is more consistent with the TFDS API:

tfds.builder('name')
tfds.builder_from_directory(path)
tfds.builder_from_directories([path,...])

PiperOrigin-RevId: 427627421

tensorflow/datasets,tensorflow/datasets,tensorflow/datasets,tensorflow/datasets,tensorflow/datasets