Integrate attribute macros into source_to_def

[jonas-schievink]

Currently, rust-analyzer does not work inside items with attribute macros when they are enabled. This is because we never add the item to the child-by-source map of the parent, because the item is replaced by the macro expansion.

This might be a bit tricky to fix, because syntactically these are still items, but semantically they're macro invocations.

[jonas-schievink]

This was mostly fixed by #9180, but it seems that fn-like macro invocations in the attribute macro's output still lose syntax highlighting and IDE functions.

[jonas-schievink]

it seems that fn-like macro invocations in the attribute macro's output still lose syntax highlighting and IDE functions.

Opened this as #10115, which has since been fixed.