ldmscon2023 dstat metrics extension

[baallan]

Automatically gathering metrics about the ldmsd itself, particularly for aggregators, is key to monitoring center-wide ldmsd hierarchy performance.
As daemon features have grown, there are other quantities of interest available at varying costs. Costs (counts) driven by user behaviors are particularly of interest, such as unique stream tags received, stream message counts, stream byte totals, and failed connections.

What other statistics are of interest, now that we have so many interactive status commands from which we might derive metrics?

The currently supported dstat metrics groups are:

fd:        Include the number of open file descriptors found in /proc/self/fd.
fdtypes:  Include the number and types of open file descriptors found in /proc/self/fd 
io:        Include the metrics from /proc/self/io.
stat:      Include the metrics from /proc/self/stat.
tick:     Include the sc_clk_tck from sysconf(3) as a metric.
statm:     Include the metrics from /proc/self/statm.
mmalloc:  Include the mmap memory usage metric from LDMS mmalloc.

[baallan]

see also: https://docs.google.com/document/d/1aoBhcosW4iIoZyMhTGjoMVkSOp5A_uDy9fDg7JuNxUE/edit#heading=h.p9zl29k6d3l0
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