lisa.tests.base: Sanitize the creation of from_target() stubs
lisa.tests.base: Sanitize the creation of from_target() stubs

Simplify the flow so that it's just a bunch of updates of attributes of the
stub, rather than arcane flipped calls to other decorators.

ARM-software/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa,credp/lisa,credp/lisa