Consider using the R Docker image to provide R Studio

[StevenMaude]

This, at time of writing, open PR adds R Studio to the OpenSAFELY R Docker image.

When that work is complete, should we switch to that image, in place of the third-party image we're currently using?

[iaindillingham]

I'm going to take this off the board and add the deck-scrubbing label. Arguably, there are more urgent and important Codespaces-related issues to work on before this.

[bloodearnest]

I am planning to pick up this ticket as part of launching r:v2 image.

[Jongmassey]

We could remove a lot of complexity from the research-template-docker build if we provide RStudio via opensafely launch rstudio rather than having to base ourselves on the Rocker images.

[Jongmassey]

Especially since #91 was found to be infeasible