In SERVER-107792, we extended the mongo test shell to support an optional logging prefix so that processes may have a "<custom prefix>:<PID>" label rather than "sh<PID>". However, the variability of the resulting format, without a familiar anchor such as "sh", does not interoperate well with tools that may expect a more predictable suffix.

In this ticket, we propose to change the format for mongo shell processes with a custom prefix to be:

sh<PID>:<custom prefix>.

On code inspection, the PID has to be the last component of the logging label, so here's a new proposed format:

sh_<custom prefix>:<PID>