Revert "WiFiSTA - allow using DHCP again after disconnecting static IP"

[JAndrassy]

I want to revert my recent PR #8848

It turned out that all libraries I tested preserved the static IP settings over disconnect() (except my WiFiEspAT). I learned that the right way to return to DHCP is config(INADDR_NONE, INADDR_NONE, INADDR_NONE). And this really worked in all WiFi libraries.
So the user of the library can config the static IP and then disconnect and later begin again with the same static IP.

[mrengineer7777]

I can see setting _useStaticIp = false; if eraseap is set. Looks like there's a lot more history behind this change I'd have to understand.

[github-actions]

	Messages
📖	You might consider squashing your 4 commits (simplifying branch history).

👋 Hello JAndrassy, we appreciate your contribution to this project!

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[VojtechBartoska]

This PR is ready to be merged as an Revert.