Merge remote-tracking branch 'upstream/stable'

Drop support for LDC v1.26.0 ...

We only support the last 10 versions, so LDC should have been upgraded in the previous PR.
In addition, we can remove a superfluous __VERSION__ statement, which haseen superfluous
for quite a while now.

Upgrade CI configuration following macOS-11 deprecation ...

macOS-11 is going away at the end of June.
As a consequence, we upgrade to macOS-12, upgrade the supported
frontend versions, and add some arm64 tests to prepare for
future upgrades.

Trivial: Remove an extra whitespace in CI file

CI: Adapt pr_info_post to github-script v7 breaking changes ...

Since v5, the method have been moved. This is not caught by CI as it
only uses the workflow in the master branch.

CI: Correct version for sticky-pull-request-comment action ...

This was not caught by CI because it doesn't take effect before merging.

CI: Upgrade some more actions to their latest versions

CI: Only attempt to upload coverage reports with COVERAGE: true ...

Otherwise we get a flurry of warning in GitHub.

Trivial: Upgrade remaining actions/checkout to v4 ...

Avoid deprecated Node 16.

Upgrade checkout and codecov to latest version ...

Get rid of a deprecation message about Node 16.

Add a CI step to upload assets on release creation ...

We haven't had assets generated for releases since v1.29.0,
however some external code depend on them (dlang-community/setup-dlang, namely).
This will fix it and make it less likely to be forgotten in the future.

Build the tests and binary with -cov on POSIX ...

The CI was sending empty coverage reports because nothing
was being generated, as the variable was always false.
In the process, a bit of dead code was removed.

CI: Move single checks to Github, remove dead code ...

Remove support for very old frontend - we were not testing it anyways.
Move the useful checks to another job so they run once.

Remove internal mentions to Travis

Re-add CodeCov support

Update supported compiler versions ...

This is to support using `-preview=in` and reducing
the amount of deprecations.

CI: Re-enable LDC master

improve github CI definitions ...

- skip CI on changes only to changelog/
- reduce permissions of GH token for PR comment

CI: Exclude some tests with DMD on Windows

CI: Enable test/run-unittest.sh on Windows

fix pr_info_post file paths

try to fix pr_info permission problem (#2621) ...

* try to fix pr_info permissions problem

* new safer pr_info

add pr_info GitHub actions run ...

Gives summary about some basic statistics, deprecations and warnings

reintroduce dmd-latest to CI runner ...

close #2199

CI: Add test for building on Alpine Linux / Musl ...

Hopefully this will prevent any regression w.r.t. Musl.

CI: Temporarily disable LDC master ...

Until the support for preview=in is fixed.

CI: Use v2.100.2 temporarily instead of latest (2.101) ...

Because 2.101 is broken with preview=in, and dub relies on it.

CI: Add some more compiler to the test suite

CI: Upgrade Ubuntu to 20.04, actions/checkout to v3

Revert "Temporarily disable ldc-master as the dustmite test is broken" ...

This partially reverts commit b1f3b03.