Add support for survival object with enter and exit time

[afarnudi]

Hi,

I developed a pipeline for the case cohort pipeline that supports survival object input with inclusion time in addition to exit time and status.

The piepline will detect if the survival object has two columns (survival::Surv(time, status)) or three columns (survival::Survival(tenter, texit, status)) in the:
"pda()",
"ODACH_CC.initialize()",
and ODACH_CC.estimate()
steps and redirect the execution to the new implementation.

Accordingly, prepare_case_cohort() was also modified to account for this change. Unfortunately, I have only implemented Prentice weights.