Fix: [AzurePipelines] switch the CI / CD to CMake too

This also means dropping Debian/jessie, as it has a CMake that is
too old (3.0), with no real path to upgrade.

Fix: [AzurePipeline] ${Agent.JobName} content changed (#7556)

* Fix: [AzurePipeline] ${Agent.JobName} content changed

* Fix: [AzurePipeline] also update commit-checker condition

Change: [AzurePipelines] Use a minimum OSX version of 10.9 during building.

OpenTTD sources are still written in a way to work down to OSX 10.4 or so, as long as you can obtain a C++11 capable compiler. 10.9 is the minimal useful C++11 target using only Apple stuff out-of-the-box.

Add: [AzurePipeline] introducing a release pipeline

This release pipeline creates all the official release binaries,
and publishes them as artifacts. Currently it can only produce
nightlies and custom builds; stable/testing release binaries are
untested.

This commit also splits up the pipeline in small bits, to both
improve readability, and to share code with the CI pipeline where
possible.

Fix: [AzurePipelines] download Windows Dependencies from GitHub Releases

It turns out that Azure Pipelines has a lot of issues downloading
an artifact from your own project if it is triggered from a fork.
From what I could deduce, this is because the API requires a valid
token, which is not set (correctly?) when triggered from a fork.
As it is nicer anyway to publish the Windows Dependencies on GitHub,
it is now published there (and updated at least every week), and
we use the files from GitHub as our dependency.