Info proc API

Summary

• .proc_version_info

• .proc_instance_info

• .proc_raft_info

• .proc_runtime_info

• fix: use compat.c_func_iproto_multireturn = 'new'

  • Note: this changes return values from all .proc_* stored procedures, making them more usable, but completely breaking the compatibility with older versions.

Part of #467 (closed)
Closes #500 (closed)

Needs sbroad!376 (merged)

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• Target branch: master
• Docs follow-up: not necessary / new issue