Use NodeKey rather than ModuleName in pruneCache

The `pruneCache` function assumes that the list of `CachedInfo` all have unique `ModuleName`, this is not true:

* In normal compilation, the same module name can appear for a file and it's boot file.
* In multiple home unit compilation the same ModuleName can appear in different units

The fix is to use a `NodeKey` as the actual key for the interfaces which includes `ModuleName`, `IsBoot` and `UnitId`.

Fixes #22677