melodie-switch: Grid search with dynamic survival metric fails

[hfrick]

With https://github.com/tidymodels/tune/tree/melodie-switch:

Grid search with a static metric works. However, if there is a dynamic metric in the metric set, things break with the error The input should have a list column called ".pred".

This breaks a whole lot of tests, probably best to start with

• tests/testthat/test-survival-fit_best.R