azure: use matrix strategy to avoid configuration redundancy
This also includes the following changes:
- Use the same timeout for all jobs on Linux (60 minutes)
and Windows (90 minutes)
- Use CLI stable apt-get install -y instead of apt install
which warns about that and run apt-get update first
- Enable MQTT for Windows msys2 builds instead of
legacy msys1 builds
- Add ./configure --prefix parameter to the msys2 builds
- The MSYSTEM environment variable is now preset inside
the container images for the msys2 builds
Note: on Azure Pipelines the matrix strategy is basically
just a simple list of job copies and not really a matrix.