After transforms, if the selected call node is not present in the call tree find a close-by call node to select

We have two transforms, `drop-function` and `filter-samples` that could remove the whole call node path. Currently we don't do anything, but ideally if the selected call node (after the transformation has been applied to the call path) is not present in the call tree, we should run some generic code that finds a close-by call node which is present.

See also #4610.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-641)