xportr_length: Set ---DTC variables length to maximum length based Date (10) or Date/Time (19)

[Ben Straub]

Update to xportr_length() that sets DTC variables to maximum length based on Date (10) or Date/Time (19) inputs.

Add a check/warning when the spec length is populated for the --DTC variables as the define.xml should not have a length (missing).

[Celine Piraux]

Reopen the issue as it is not yet implemented. To much issues with DTC variables 😅