Docs for SERVER-36380: Add CLI option for dumping config as YAML

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Original Description

Description:

Documentation depends on whether or not we normally document hidden command line options.

When --outputConfig is passed to mongod or mongos, the resolved configuration will be dumped to stdout and the server instance will halt.

This will allow diagnosis of configuration issues by yielding a single, authoritative configuration file.

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Description

Scope of changes (files that need work and how much)

Impact to other docs outside of this product

MVP (work and date?)

Resources (e.g. Scope Docs, Invision)