Tier 2 targets

Co-authored-by: Guillaume Gomez <guillaume1.gomez@gmail.com>

Hermit rwlocks are movable.

Hermit condvars are movable.

Hermit mutexes are movable.

Also fixed capitalization of documentation

…sts, r=GuillaumeGomez

Run rustdoc-gui tests in parallel

I hid the passing tests and only show the failed ones in alphabetical order:
![image](https://user-images.githubusercontent.com/739070/123663020-84e63100-d825-11eb-9b35-0a8c30cd219c.png)

Also this PR cuts down the execution time from ~40 to ~9 seconds

…bini

Adding explicit notice of lack of documentation for Tier 2 Platforms

Fixing: rust-lang/rustup#2788

…bini

Remove git fetch from CI

rust-lang#86623 added a call to `git fetch`, which is problematic for releases.

r? `@pietroalbini`

…pans, r=cjgillot

Detect fake spans in non_fmt_panic lint.

This addresses rust-lang#87621

Some proc_macros claim that the user wrote all of the tokens it outputs, by applying a span from the input to all of the produced tokens. That can result in confusing suggestions, as in rust-lang#87621. This is a simple patch that avoids suggesting anything for `panic!("{}")` if the span of `"{}"` and `panic!(..)` are identical, which is normally not possible.

…=cjgillot

Add automatic migration for assert!(.., string).

Fixes part of rust-lang#87313.

Forbid `!` from being used in `asm!` output

Fixes rust-lang#87802

r? `@Amanieu`

Unbox mutexes, condvars and rwlocks on hermit

[RustyHermit](https://github.com/hermitcore/rusty-hermit) provides now movable synchronization primitives and we are able to unbox mutexes and condvars.

Assign FIXMEs to me and remove obsolete ones

Also fixed capitalization of documentation

We also don't need to transform predicates to be non-const since we basically ignore const predicates in non-const contexts.

r? `@oli-obk`