Migrate to `FormData`

[AuHau]

Currently, when uploading collection in any form (eq. using uploadCollection or uploadFiles etc.) it might seems like the user can specify entry's content type (e.g. using the new File(..., ..., {type: 'come content type'})), which then, unfortunately, is ignored because we use Tar way how to upload collection (in Bee then the content type is guessed based on extension).

As soon as ethersphere/bee#2578 is solved I would like to migrate uploading collection using FormData which then would allow this to be solved.