Fix rustc_ast_pretty print_qpath resulting in invalid macro input

related rust-lang#76874 (third case)

### Issue:

The input for a procedural macro is incorrect, for the rust code:
```rust

mod m {
    pub trait Tr {
        type Ts: super::Tu;
    }
}

trait Tu {
    fn dummy() { }
}

#[may_proc_macro]
fn foo() {
    <T as m::Tr>::Ts::dummy();
}
```
the macro will get the input:
```rust
fn foo() {
    <T as m::Tr>::dummy();
}
```
Thus `Ts` has disappeared.

### Fix:

This is due to invalid pretty print of qpath. This PR fix it.

Fix rustc_ast_pretty print_qpath resulting in invalid macro input

related rust-lang#76874 (third case)

### Issue:

The input for a procedural macro is incorrect, for the rust code:
```rust

mod m {
    pub trait Tr {
        type Ts: super::Tu;
    }
}

trait Tu {
    fn dummy() { }
}

#[may_proc_macro]
fn foo() {
    <T as m::Tr>::Ts::dummy();
}
```
the macro will get the input:
```rust
fn foo() {
    <T as m::Tr>::dummy();
}
```
Thus `Ts` has disappeared.

### Fix:

This is due to invalid pretty print of qpath. This PR fix it.

Fix rustc_ast_pretty print_qpath resulting in invalid macro input

related rust-lang#76874 (third case)

### Issue:

The input for a procedural macro is incorrect, for the rust code:
```rust

mod m {
    pub trait Tr {
        type Ts: super::Tu;
    }
}

trait Tu {
    fn dummy() { }
}

#[may_proc_macro]
fn foo() {
    <T as m::Tr>::Ts::dummy();
}
```
the macro will get the input:
```rust
fn foo() {
    <T as m::Tr>::dummy();
}
```
Thus `Ts` has disappeared.

### Fix:

This is due to invalid pretty print of qpath. This PR fix it.

Rollup of 15 pull requests

Successful merges:

 - rust-lang#78352 (Do not call `unwrap` with `signatures` option enabled)
 - rust-lang#78590 (refactor: removing alloc::collections::vec_deque ignore-tidy-filelength)
 - rust-lang#78848 (Bump minimal supported LLVM version to 9)
 - rust-lang#78856 (Explicitly checking for or-pattern before test)
 - rust-lang#78948 (test: add `()=()=()=...` to weird-exprs.rs)
 - rust-lang#78962 (Add a test for r# identifiers)
 - rust-lang#78963 (Added some unit tests as requested)
 - rust-lang#78966 (Never inline C variadics, cold functions, functions with incompatible attributes ...)
 - rust-lang#78968 (Include llvm-as in llvm-tools-preview component)
 - rust-lang#78969 (Normalize function type during validation)
 - rust-lang#78980 (Fix rustc_ast_pretty print_qpath resulting in invalid macro input)
 - rust-lang#78986 (Avoid installing external LLVM dylibs)
 - rust-lang#78988 (Fix an intrinsic invocation on threaded wasm)
 - rust-lang#78993 (rustc_target: Fix dash vs underscore mismatches in option names)
 - rust-lang#79013 (Clean up outdated `use_once_payload` pretty printer comment)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup