The QMP monitor provides a number of commands for querying info about
the QEMU binary capabilities. Given that these commands don't take
any options and just return static data, requiring the use of QMP is
unnecessarily onerous. This adds a new '-capabilities' command line
argument as a syntactic sugar for accessing the QMP commands that
just return static QEMU binary capabilities.
Setting the '-capabilities' argument causes QEMU to output the requested
data on stdout, pretty printed in JSON format. The argument expects an
associated value to identify the data to be printed. This can be one of
the strings version|machines|devices|cputypes|target|commands|argv|netdev
To query all possible data at once, the shorthand 'all' is allowed.
The output is a QDict where the key is the type of data requested, and
the value is the JSON data from the associated monitor command. For
example: