11894: complete pattern args based on type name r=Veykril a=cameron1024
Addresses #11892
Changes function argument completion to cover a case like this:
```rust
struct Foo { bar: i32 }
fn qux(Foo { bar }: Foo) {
println!("{bar}");
}
```
When completing the function call for `qux`, instead of expanding to `qux(_)`, it will now expand to `qux(foo)` (based on the snake-cased version of the name of the ADT)
Non ADTs are unaffected
Co-authored-by: cameron <cameron.studdstreet@gmail.com>
Co-authored-by: cameron1024 <cameron.studdstreet@gmail.com>
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