The `assays(TreatmentResponseExperiment)` method is really slow in WSL2

The `assays` method for a `TreatmentResponseExperiment` is taking a long time (~4s) to execute on WSL2 with 2 `data.table` threads.

Need to assess if this occurs on other platforms? 

Could possibly speed up the internal joins with `colData` and `rowData` by keying the `data.table`s.

Definitely need to look at improving the speed.

Best,
Chris