v0.26.1: Update CI on the stable-v0.26 branch (#2921)

* Try to fix CI (#2918)

Fixes a few issues that have been cropping up:

* Update `rustup` on Windows to latest to skip over the 1.24.1 installed
  on GitHub Actions which can fail to install.
* Remove the no-longer-needed `define-llvm-env` action
* Install generic llvm/lldb packges instead of specific ones that may
  migrate in versions over time.

* cargo deny: ignore RUSTSEC-2021-0064

Transient dependencies depend on two different versions of `cpuid-bool`.

This advisory does not appear to be urgent. We should review this ignore
after a few weeks to see if our deps have switched over.

text of the advisory:

Issued
May 6, 2021
Package
cpuid-bool (crates.io)
Type
Unmaintained
Details
https://github.com/RustCrypto/utils/pull/381
Patched
no patched versions
Description
Please use the `cpufeatures`` crate going forward:

https://github.com/RustCrypto/utils/tree/master/cpufeatures

There will be no further releases of cpuid-bool.

* Run CI on this branch

Co-authored-by: Pat Hickey <pat@moreproductive.org>

v0.26.0: Merge pull request #2805 from cfallin/release-0.26.0

Release 0.26.0.

v0.25.0: Merge pull request #2731 from fitzgen/make-0.25.0-release

Make 0.25.0 release

v0.24.0: Bump version to 0.24.0

I used a specially modified version of the publish script to avoid
bumping the `witx` version.

v0.23.0: Bump version to 0.23.0

I used a specially modified version of the publish script to avoid
bumping the `witx` version.

v0.22.1

Bump smallvec dependency to 1.6.1

v0.22.0: Merge pull request #2557 from fitzgen/wasmtime-0.22.0

Wasmtime 0.22.0

v0.21.0

Bump to 0.21.0 (#2359)

v0.20.0

Add metadata to peepmatic crates (#2245)

v0.19.0: Wasmtime 0.19.0 and Cranelift 0.66.0 (#2027)

This commit updates Wasmtime's version to 0.19.0, Cranelift's version to
0.66.0, and updates the release notes as well.