fix: networkmanager cannot be started within OnClientStopped or OnServerStopped callbacks

[NoelStephensUnity]

Purpose of this PR

Based on a user submitted issue, adding the ability to start NetworkManager from within NetworkManager.OnClientStopped or NetworkManager.OnServerStopped.

If a host starts itself within the NetworkManager.OnClientStopped, then it will skip invoking the NetworkManager.OnServerStopped since it will have already been started again.

fixes: #2703

Jira ticket

MTT-10150

Changelog

• Fixed: If a user starts NetworkManager from within one of its stopped callbacks at the end of shutdown it will fail to start properly.

Documentation

• Includes edits to existing public API documentation.

Testing & QA (How your changes can be verified during release Playtest)

Functional Testing

Manual testing :

• Manual testing done

Automated tests:

• Covered by existing automated tests
• Covered by new automated tests

Does the change require QA team to:

• Review automated tests?
• Execute manual tests?
• Provide feedback about the PR?

If any boxes above are checked the QA team will be automatically added as a PR reviewer.

Backports

No backport. This will be v2.x specific.

[EmandM]

This is huge!

[jabbacakes]

Mostly just wording tweaks. Main change is moving the info about pre-shutdown notifications to the bottom of its section. It makes more sense to me to introduce the 'you will definitely want to do this' info first, and then add the if statement of 'and you can also do this if you need something else'.