Add android_logger_get_log_consumed_size() and report it in logcat

There is an existing API, android_logger_get_log_readable_size() which
historically reported the consumed amount of data for the chatty log
buffer, since consumed and readable are synonymous with that buffer
type.

With log compression, readable and consumed are not synonymous, since
the readable log size is the uncompressed log size whereas the
consumed log size is the compressed log size.

This change adds android_logger_get_log_consumed_size() which returns
the consumed log size and makes android_logger_get_log_readable_size()
return the readable log size.  Note that these values are identical if
compression is not used.

It adds both statistics to logcat:

    main: ring buffer is 1 MiB (429 KiB consumed, 817 KiB readable)
    radio: ring buffer is 1 MiB (339 KiB consumed, 715 KiB readable)
    ...

Test: logcat prints the right values with compression and chatty
Change-Id: I8b9688a987736204e2e6026e8635fbd1a5e68bb7