Fix memory_breakdown for connection procs

[lhoguin]

Instead of trying to read the ranch_server ETS table directly,
use an internal Ranch function that does the same. While neither
are documented, the latter is less likely to change.

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[lhoguin]

Recent push is a rebase to fix conflicts in release notes.

[michaelklishin]

I could reproduce the issue and verified that the fix works as expected. Note that we will have to backport this to v3.8.x manually because v3.8.x does not have 3.9 release notes.

[lhoguin]

Oh alright. :-)