11201: fix: Fix completions not considering ancestor items for attribute search r=Veykril a=Veykril
Turns out we never filled the `CompletionContext` with the attribute expansion of attributed impls and traits when typing in the assoc items, as we were only considering the assoc item to have an attribute to expand.
bors r+
Co-authored-by: Lukas Wirth <lukastw97@gmail.com>