* feat(admin): add profiling options for debugging high memory/CPU usage
Add -debug, -debug.port, -cpuprofile, and -memprofile flags to the admin
command, matching the profiling support already available in master, volume,
and other server commands. This enables investigation of resource usage
issues like #8919.
* refactor(admin): move profiling flags into AdminOptions struct
Move cpuprofile and memprofile flags from global variables into the
AdminOptions struct and init() function for consistency with other flags.
* fix(debug): bind pprof server to localhost only and document profiling flags
StartDebugServer was binding to all interfaces (0.0.0.0), exposing
runtime profiling data to the network. Restrict to 127.0.0.1 since
this is a development/debugging tool.
Also add a "Debugging and Profiling" section to the admin command's
help text documenting the new flags.