tests: Move the tests/data and tests/guests directories to test-data.

Create a new top-level directory called test-data, which will carry
all the test data which is large and/or shared between multiple tests.

There are actually several new subdirectories created:

test-data/binaries: The pre-built binary and library files for random
architectures that we use to test various architecture detection
features (was part of tests/data).

test-data/blank-disks: The blank disks which are used for disk format
detection (was part of tests/data).

test-data/files: Other miscellaneous test files from tests/data that
are not included in the above.

test-data/phony-guests: The phony guests (was tests/guests).

test-data: The top-level directory builds the 'test.iso' image file
that is used for testing the C API and in miscellaneous other tests.

python/run-python-tests

@@ -18,7 +18,7 @@
 
 errors=0
 
-guestsdir="$(cd ../tests/guests && pwd)"
+guestsdir="$(cd ../test-data/phony-guests && pwd)"
 export guestsdir
 
 for f in $srcdir/t/*.py; do