Fix wrong script info used to resolve line/offset for call hierarchy

[rbuckton]

This fixes two issues with call hierarchy:

• When preparing a call hierarchy item we were incorrectly using the script info for the file at the current cursor position when resolving line/character for item's declaration, which could be in another file.
• When resolving incoming calls, we were incorrectly using the script info for the current call hierarchy item rather than the script info for the file containing the incoming declaration.

Note that the current behavior for outgoing calls is correct (it uses the script info for the current call hierarchy item).

Fixes #36509
Fixes #36512