Rework manual AdqReduce options

Based on experience with applying AdqReduce to more proposals, this MR reworks the manual options offered by this plugin:

• Change --adq-remove-output <modes> to more general --adq-remove-explicit <sources>,<modes>,<channels>
• Change --adq-always-preserve <sources>,<channels> to --adq-always-preserve <sources>,<modes>,<channels>
• Apply preserved channels also to explicitly removed channels

Channels are also referred to without the underscore now, and fix a couple of smaller issues.