tests/functional: Convert the 32-bit big endian Wheezy mips test

tests/functional: Convert the 32-bit big endian Wheezy mips test

The test checks some entries in /proc and the output of some commands ...
we put these checks into exportable functions now so that they can
be reused more easily.

Additionally the linux_ssh_mips_malta.py uses SSH to test the networking
of the guest. Since we don't have a SSH module in the functional
framework yet, let's use the check_http_download() function here instead.

And while we're at it, also switch the NIC to e1000 now to get some more
test coverage, since the "pcnet" device is already tested in the test
test_mips_malta_cpio.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20250414113031.151105-7-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>