qemu: monitor: Implement HMP version for listing all block device stats

qemu: monitor: Implement HMP version for listing all block device stats

Add a different version of parser for "info blockstats" that basically
parses the same information as the existing copy of the function.

This will allow us to remove the single device version
qemuMonitorGetBlockStatsInfo in the future.

The new implementation uses few new helpers so it should be more
understandable and provides a test case to verify that it works.