Add AP3211 DC-DC Step-Down

Revival of !3454 (closed), finishing the description and reordering pins so it is pin-compatible with AP63200WU

Datasheet: https://www.diodes.com/assets/Datasheets/AP3211.pdf

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• Remove the instructional content of this template
• Provide a URL to a datasheet for the symbol(s) you are contributing
• An example screenshot image is very helpful
• Ensure that the associated footprints match the official footprint library
  • A new fitting footprint must be submitted if the library does not yet contain one.
• Check the output of the automated check scripts - fix any errors as required