Refactor server chat handling by extracting methods

[dingodoppelt]

Short description of changes

This refactors CServer::CreateAndSendChatTextForAllConChannels into three functions for sending messages.
The extracted methods

1. create the full chat message including timestamp and name of the sending client,
2. iterate over all possible channel numbers to
3. send the message text to a channel

As it is now possible to call the function to send a message to a channel directly, the channel number needs to be boundary checked.
A function InRange() was introduced into util.h for that purpose.

CHANGELOG: Refactor server chat handling by extracting methods

Context: Fixes an issue?

Not yet ;)

Does this change need documentation? What needs to be documented and how?
No

Status of this Pull Request

Ready for review
What is missing until this pull request can be merged?

Review, Approval

Checklist

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