dotest: Add a way for the run_to_* helpers to register dylibs
To run the testsuite remotely the executable needs to be uploaded to
the target system. The Target takes care of this by default.
When the test uses additional shared libraries, those won't be handled
by default and need to be registered with the target using
Calling this API requires a target, so it doesn't mesh well with the
run_to_* helpers that we've been advertising as the right way to write
This patch adds an extra_images argument to all the helpers and does
the registration automatically when running a remote
testsuite. TestWeakSymbols.py was converted to use this new scheme.
Differential Revision: https://reviews.llvm.org/D70134