"Select a Biomarker" menu item construction.

### Feature description

1. seems that there is a validation that the analysis variable has to be PARAMCD but PARAM would work equally well. Can PARAM be added to the validation so that it too is acceptable as this argument? param_var = "PARAM"?
2. If above is acceptable then we need to deal with the menu item sorting. currently the sort looks like a regular case sensitive sort by ASCII collating sequence so upper case sorts first then lower case. but what we want is a case insensitive sort like in the following example
```
# Sample vector
my_vector <- c("apple", "Banana", "cherry", "Date")

# Perform case-insensitive sorting
sorted_vector <- my_vector[order(tolower(my_vector))]

# Display the sorted vector
print(sorted_vector)

```
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Locate the code that constructs the "Select a Biomarker" menu and validates the analysis variable. Check how PARAMCD is currently accepted, then verify that PARAM is also valid and that menu entries sort case-insensitively. Done means both variable names work and the menu ordering matches the requested behavior.

Written by the indexing model from the issue text.