Merge #10602

10602: Add qualify method call assist r=Veykril a=qepasa

This adds `qualify_method_call` assist that allows to replace a method (or trait) call that resolves with its fully qualified path.

For example, for stuct method:
```rust
struct Foo;
impl Foo {
    fn foo(&self) {}
}
```
```
let foo = Foo {};
foo.fo$0o();
```

becomes
```rust
let foo = Foo {};
Foo::foo(&foo);
```

for a trait method:

```rust
struct Foo;
trait FooTrait {
    fn foo(&self) {}
}
impl FooTrait for Foo {
    fn foo(&self) {}
}
```
following call:
```rust
let foo = Foo {};
foo.fo$0o();
```

becomes:
```rust
let foo = Foo {};
FooTrait::foo(&foo);
```

fixes #10453 

Co-authored-by: Paweł Palenica <[email protected]>

Author: bors[bot]