[MC2DP-908] Add R packages and R_LIBS_USER for user-installable libs in jupyter-rcc

[wangfan860]

Link to JIRA ticket if there is one: https://ctds-planx.atlassian.net/browse/MC2DP-908

New Features

1. Preinstalled R packages

The following are now available out of the box:

devtools, broom, comorbidity, survival, data.table, dplyr, fst,
lubridate, magrittr, MASS, pbapply, reshape2, stringi, stringr,
sqldf, tableone, xlsx, testthat (3.2.3, requirement was >= 2.1.0)

2. Users can now install their own R packages

Previously install.packages('foo') failed in the R kernel with
lib = "/usr/local/lib/R/site-library" is not writable, because that directory
is root-owned and the workspace runs as jovyan. Outside of IRkernel, R would
normally offer to create a personal library, but that prompt cannot work in a
notebook, so it just errored out.

This PR sets R_LIBS_USER=/home/jovyan/pd/r_libraries in the image, and creates
that directory in start-notebook.sh. Users can now do:

install.packages('maftools')
# Kernel -> Restart Kernel
library(maftools)