build-test-uefi: convert the existing distro build script to uefi test script

The existing distro boot test script does nothing more than building
all the software components that are required to test booting to a
uefi shell. So rename the distro boot script as a uefi boot test
script.

Change-Id: I2959d96a5633e7aef393719deef5f63d22e18d7e
Signed-off-by: Thomas Abraham <thomas.abraham@arm.com>