This fixes an ICE when building libcore with `-Z mir-opt-level=3`.

Emit StorageDead along unwind paths for generators

Completion of the work done in #60840. That PR made a change to implicitly consider a local `StorageDead` after Drop, but that was incorrect for DropAndReplace (see also #61060 which tried to fix this in a different way).

This finally enables the optimization implemented in #60187.

r? @EddyB
cc @Zoxc @cramertj @RalfJung

Implementation of RFC 2289 (associated_type_bounds)

This PR implements the [`asociated_type_bounds` feature](https://github.com/rust-lang/rfcs/blob/master/text/2289-associated-type-bounds.md).

Associated type bounds are implemented in:
   - function/method arguments and return types
   - structs, enums, unions
   - associated items in traits
   - type aliases
   - type parameter defaults
   - trait objects
   - let bindings

CC @nikomatsakis @centril

Refactor `TypeVariableOrigin`

Removes some unused variants and extracts the common `Span` field.

As suggested in https://github.com/rust-lang/rust/pull/59008#discussion_r265031209.

r? @EddyB

Rollup of 5 pull requests

Successful merges:

 - #61503 (Fix cfg(test) build for x86_64-fortanix-unknown-sgx)
 - #61534 (Edit docs of ExitStatus)
 - #61536 (Don't allow using const fn arguments as "args_required_const")
 - #61538 (Don't use GNU noexec stack note)
 - #61546 (azure: Fix some minor issues which have broken our configuration )

Failed merges:

r? @ghost

azure: Fix some minor issues which have broken our configuration

* Ensure that when we enable IPv6 for Docker on Linux that the various directories before writing a config file
* Delete a previously installed rustup if any since it seems to interfere with Cargo's test suite.

Don't use GNU noexec stack note

NetBSD ignores this note and marks the stack no-exec unconditionally

Don't allow using const fn arguments as "args_required_const"

r? @EddyB

Edit docs of ExitStatus

The documentation of [`ExitStatus`] are extended to be at the same depth as [`Output`].

Fix cfg(test) build for x86_64-fortanix-unknown-sgx

Add "type_name" support in emulate_intrinsic()

I did some dumb Git things and deleted my original fork repo semi-accidentally (but probably for the best as I'd messed up the history.)

This is the same issue as #61399, which was obviously auto-closed, to be clear.