Run clang-tidy modernize-use-override to remove all the redundant
virtual keywords from overridden methods, and add some missing
overrides.
Another benefit is that this has also added the overrides
on destructors, which will cause a build failure if a base
class is missing a virtual destructor.
- take a clone of algs before running them. This avoids issues
if the algorithm is removed or edited while a background task
is running
- accept an optional existing feedback object
