Enhancement: refactor pivot_wider_pknca_results

[Gero1999]

Description

In order to simplify the final script looking (#467) and simplify the workflow, it would be good to:

1. internalize the flagged column creation inside this function. use the options of the PKNCAdata object to "re-create" the FLAG_RULES. This will need some updated from PKNCA, as they still not include some of our criterias as options for the user for the flag rules (Collaboration: Things to consider for next PKNCA update #481)

2. internalize parameters pivoted to only include the ones requested from the user. It is easier to be done before pivoting.

3. for the grouping_vars, it should be internalized (probably already done in Create R script to replicate App outputs (#467) #789). And preferably groupping vars mapped through keep_interval_cols so this can be more automatized.

Definition of Done

• pivot_wider_pknca_results can create the flagged column
• if PKNCA handles in their options all setups, no need to use FLAG_RULES in nca_results.R. Just take from the results obj the rules.
• pivot_wider_pknca_results already can remove parameters not explicitely requested
• grouping vars arg for the function using keep_interval_cols or something easy to automatize