phrase_len is not called phrase_length
Allow awareness attributes to be reset via the API

Currently we don't allow resetting the awareness
attribute via the API since it requires at least one
non-empty string to update the setting. This commit
allows resetting this using an empty string.

Closes #3931
Document strict dynamic type mapping.
Fix small typo in terms lookup tests mapping.
Fix small typo in terms lookup tests mapping (count api tests)
[DOCS] Reorganised the highlight_query docs and added a version flag