The std::run module is a relic from a standard library long since past, and
there's not much use to having two modules to execute processes with where one
is slightly more convenient. This commit merges the two modules, moving lots of
functionality from std::run into std::io::process and then deleting
std::run.

New things you can find in std::io::process are:

* Process::new() now only takes prog/args
* Process::configure() takes a ProcessConfig
* Process::status() is the same as run::process_status
* Process::output() is the same as run::process_output
* I/O for spawned tasks is now defaulted to captured in pipes instead of ignored
* Process::kill() was added (plus an associated green/native implementation)
* Process::wait_with_output() is the same as the old finish_with_output()
* destroy() is now signal_exit()
* force_destroy() is now signal_kill()

Closes #2625
Closes #10016

fix: f32 and f64 representation during lowering

should fix rust-lang#12380

[`redundant_closure_call`]: Don't lint if closure origins from a macro

The following code used to trigger the lint:
```rs
 macro_rules! make_closure {
     () => {
         (|| {})
     };
 }
 make_closure!()();
```
The lint would suggest to replace `make_closure!()()` with `make_closure!()`, which changes the code and removes the call to the closure from the macro. This commit fixes that.

Fixes rust-lang#12358

----

changelog: [`redundant_closure_call`]: If `x!()` returns a closure, don't suggest replacing `x!()()` with `x!()`