feat(developer): Move options to ~/.keymandeveloper/options.json

Fixes #10161.

Includes transition of existing options from registry to options.json,
and once options.json exists, will always read from that and ignore
registry. Was able to eliminate some of the legacy datatype usage for
several options. Reader/writer includes naive file lock retry to avoid
contention, which I am hopeful will be sufficient for our needs, given
the low chance of contention.