Collect tokens for inner attributes at crate or outline module root

[Aaron1011]

Currently, custom inner attributes at the crate or outline module root do not have tokens collected:

rust/compiler/rustc_expand/src/expand.rs

Lines 718 to 728 in 5c13042

	if let Annotatable::Item(item_inner) = &item {
	if let ItemKind::Mod(_, mod_kind) = &item_inner.kind {
	// FIXME: Collect tokens and use them instead of generating
	// fake ones. These are unstable, so it needs to be
	// fixed prior to stabilization
	// Fake tokens when we are invoking an inner attribute, and:
	fake_tokens = matches!(attr.style, ast::AttrStyle::Inner) &&
	// We are invoking an attribute on the crate root, or an outline
	// module
	(item_inner.ident.name.is_empty() || !matches!(mod_kind, ast::ModKind::Loaded(_, Inline::Yes, _)));
	}

This means that code like:

#![my_attr]

struct Foo {}
fn bar() {}

will cause us to lose spans for the entire crate root / outline module. The token streams in question are never nested 'inside' something else, so we might not need the full logic in collect_tokens_trailing_token to handle this case.

Custom inner attributes are currently unstable, so this needs to be fixed prior to stabilization in the crate root / outline module root position.