General Issue: move roxygen_param_by_vars() from admiral to admiraldev

[bms63]

Background Information

roxygen_param_by_vars() is an experimental function to help standardize common arguments text across admiral functions. IT seems to be working well and should be brought into admiraldev as it is more geared towards developers.

Definition of Done

• Move roxygen_param_by_vars() and tests files to admiraldev
• Enhance documentation (there is very little)
• Ensure test coverage is 100%
• Identify other opportunities to utilize this function in admiral

@pharmaverse/admiral a fun one to work on