fix: resolve doc path from parent module if outer comments exist on module

[Hmikihiro]

fix: #19506
#19471

I set placement information about inner or outer in attribute.
When I check link on module, I search from parent module if attribute of doc item have a outer comment.

[Veykril]

This grows attributes by 8 bytes which will be noticable, we'll need to avoid that somehow if we can. Note quite sure how yet. Probably by using one of the AttrId bits (we already do something there for cfg_attr but that is not really used so we can replace that with this likely). Will write oiut better instructions later

[Hmikihiro]

rust-analyzer/crates/hir-expand/src/attrs.rs

Lines 185 to 189 in 588948f

	impl AttrId {
	const CFG_ATTR_BITS: usize = 7;
	const AST_INDEX_MASK: usize = 0x00FF_FFFF;
	const AST_INDEX_BITS: usize = Self::AST_INDEX_MASK.count_ones() as usize;
	const CFG_ATTR_SET_BITS: u32 = 1 << 31;

Right, that means AttrId currently uses bits like this:

• Bit 31 → is_cfg_attr
• Bits 24–30 → cfg_attr_index (7 bits)
• Bits 0–23 → ast_index (24 bits)

So, we could either remove or reduce the size of cfg_attr_index, and reuse the freed bit for placement information.

• Bit 31 → inner_or_outer
• Bits 24–30 → (unused)or (is_cfg_attr & cfg_attr_index(6bit))
• Bits 0–23 → ast_index

[Hmikihiro]

rust-analyzer/crates/hir-expand/src/attrs.rs

Lines 108 to 110 in 588948f

	let mut it = it.clone();
	it.id.id = (it.id.ast_index() as u32 + last_ast_index)
	| ((it.id.cfg_attr_index().unwrap_or(0) as u32)

And cfg_attr was accessed through cfg_attr_index() but this function was only used to copy it when creating a new [Attr]. So would we remove cfg_attr?