When the 'fields' setting is not set in htoprc, the htop program won't read any
of the settings. Provide a default value for fields in case it's not explicitly
set by the user.
* htop: add some missing meters
* htop: replace individual options with 'settings'
Deprecate all options and introduce `settings` for setting htop configuration
values in Nix configuration.
Use `lib.htop` to provide `fields` and `modes` for easy access to htop's integer
configuration. And `leftMeters` and `rightMeters` functions for building the
separate `*_meters` and `*_meter_modes` attributes.
* htop: add release-notes 21.05 entry
* htop: improve deprecation warnings
Move default configuration into `settings` and make deprecated options default
to `null`. Print deprecation warnings for any option that is non-null --
i.e. only show warnings for explicitly specified deprecated options.
* htop: make self code owner of module
* release notes: fix invalid programs.htop xref
