Pepper "samples_dropped" attributes into appropriate facile_frame manipulation functions

[lianos]

When querying a multi-modal FacileDataStore, there are times when you have facile_frame used as an input to a function, which also takes an "assay_name" parameter.

It's possible that the samples you put in don't all have assay data from "assay_name" and the result you get back will either have NA values, or it drops the samples with missing assay data altogether.

I've introduced a drop_samples = TRUE parameter to these functions, which is to say that the default behavior is to just drop the samples that don't have the assay data. The dropped samples are returned in an attr(out, "samples_dropped") attribute

You can get the samples that were dropped in such a way by calling samples(out, dropped = TRUE)

The fetch_assay_data.FacileDataSet@multi-modal-unit-testing [link] and assay_sample_info.FacileDataSet@multi-modal-unit-testing [link] give you an idea of what we're talking aboot.