Add doc-alias based completion
Closes#14406.
I adapted the parsing code from the CfgExpr parsing code, maybe there's a better abstraction for both, or attribute parsing in general. It also includes `doc(hidden)`-parsing, which means it could replace the other function.
There are a few tests for parsing.
`process_all_names` changed the most, I added some docs there to explain what happens.
Many call sites just pass an empy vec to `add_path_resolution`'s `doc_aliases`, since either it doesn't make sense to pass anything (e.g. visibility completion) or I don't know where to get them from. Shouldn't really matter, as it will just not show aliases if the vec is empty and we can extend alias completion in these cases later.
I added two tests in `special.rs` for struct name completion (which was the main thing I wanted). I also tried function and field names, but these don't work yet. I want to add those in a follow-up PR.
feat: show only missing variant suggestion for enums in patterns completion and bump them in list too
Fixes#12438
### Points to help in review:
- This PR can be reviewed commit wise, first commit is about bumping enum variant completions up in the list of completions and second commit is about only showing enum variants which are not complete
- I am calculating missing variants in analysis.rs by firstly locating the enum and then comparing each of it's variant's name and checking if arm string already contains that name, this is kinda hacky but I didn't want to implement complete missing_arms assist here as that would have been too bulky to run on each completion cycle ( if we can improve this somehow would appreciate some inputs on it )
### Output:
https://user-images.githubusercontent.com/49019259/208245540-57d7321b-b275-477e-bef0-b3a1ff8b7040.mov
Relevant Zulip Discussion: https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Frust-analyzer/topic/Issue.20.2312438
fix: breaking snippets on typed incomplete suggestions
Possible fix for #7929
Fix the case where if a user types `&&42.o`, snippet completion was still applying &&Ok(42). Note this was fixed previously on `&&42.` but this still remained a problem for this case
Previous relevant PR: #13517
### Points to help in review:
- The main problem why everything broke on adding an extra `o` was, earlier `dot_receiver` was `42.` which was a `LITERAL` but now `42.o` becomes a `FIELD_EXPR`
- Till now `include_references` was just checking for parent of `LITERAL` and if it was a `REF_EXPR`, but now we consider `FIELD_EXPR` and traverse all of them, finally to reach `REF_EXPR`. If `REF_EXPR` is not found we just return the original `initial_element`
- We are constructing a new node during `include_references` because if we rely on `dot_receiver` solely we would get `&&42.o` to be replaced with, but we want `&&42` to be replaced with
### Output Video:
https://user-images.githubusercontent.com/49019259/205420166-efbdef78-5b3a-4aef-ab4b-d892dac056a0.mov
Hope everything I wrote makes sense 😅
Also interestingly previous PR's number was `13517` and this PR's number is `13715`, nicee
Fix the case where if a user types `&&42.o`, snippet completion
was still applying &&Ok(42). Note this was fixed previously
on `&&42.` but this still remained a problem for this case
