migrate `**opts` to native kwargs for most commands

These were fairly trivial, but a step towards consistency. Other methods would be more involved, or alternately were even more trivial (i.e. less than a screenful of code, and one use of opts, where it needed to be byteskwargs), so a simple move didn't seem worthwhile. The extensions need this next, and then some internal APIs can be done. There probably needs to be a plan for internal APIs, both for compatibility of 3rd party stuff before and after the switch, but also because some APIs have grown additional arguments after opts, and so can't be converted to **opts trivially.