OvmfPkg: CI: Use Fedora 35 container (Linux only)

OvmfPkg: CI: Use Fedora 35 container (Linux only)

Run the Linux jobs of the OvmfPkg platform CI inside a container,
in the same way the general CI does now. Make use of the default image
specified in the defaults.yml template.

Do not run apt-get in CI jobs to install qemu and gcc dependencies.
Assume the container image provides these.

Use Python from the container image, do not download at runtime.

Signed-off-by: Oliver Steffen <osteffen@redhat.com>
Acked-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Michael Kubacki <michael.kubacki@microsoft.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Chris Fernald <chfernal@microsoft.com>