* Added per-field size details.
This also does a bunch of refactoring.
merging field metadata does not silently asserts that arguments should be sorted.
merging does not set `stored`.
We do not rely on a hashmap to group fields, but instead rely on the fact that
the term dictionary is sorted.
The inverted level method that exposes field metadata is not exposed
as public anymore.
* CR comment
---------
Co-authored-by: Paul Masurel <paul.masurel@datadoghq.com>
* Fix trait bound of StoreReader::iter
Similar to `StoreReader::get`, `StoreReader::iter` should only require
`DocumentDeserialize` and not `Document`.
* Mark the iterator returned by SegmentReader::doc_ids_alive as Send so it can be used in impls of Stream/AsyncIterator.
