[FEATURE REQUEST] add emitter_kwargs to optimizer ask and tell

[btjanaka]

Description

In order to make ask and tell more flexible, we can add emitter kwargs that get passed in. If the kwargs is a single dict, we pass those kwargs to all the emitters. If it is a list of dicts, each entry holds kwargs for one emitter.

[btjanaka]

Added in #159 but reverted in #167 as we are still thinking about the behavior of this feature -- for instance, what if we had emitters that take in an argument but other emitters that did not take in the argument, but we did not want to have to duplicate the kwargs in a list?