Add support for new unphone boards

[garethhcoleman]

Second time doing this - accidentally closed previous #7058 in error!

Is adding a new partition scheme acceptable?

Please advise if any changes or clarification needed.

Thanks!

Description of Change:
Adds two new pin maps for the unPhone spin 8 and spin 9 to variants/unphone8 and variants/unphone9
Updated boards.txt to add definitions for unphone7 (based on Adafruit ESP32 feather) and unphone 8 and 9 (ESP32-S3)
Added a new partition scheme for 8MB flash variant of ESP32-S3 with maximum program size (7.9MB)

Tests scenarios:
Tested on our prototype hardware with a variety of test sketches, pin assignments seem correct.

Related links:
Hardware description at unphone.net and software at https://gitlab.com/hamishcunningham/unphone

[SuGlider]

@garethhcoleman - It seems that unphone7 is missing pins_arduino.h in Variants. Please let me know.

[garethhcoleman]

@SuGlider Yes, you are correct.
We based the unphone7 on the esp32 feather so closely, they share pin definitions.
Therefore, we have unphone7.build.variant=feather_esp32
This works in our testing, please advise if this is acceptable to you, happy to create a copy if required.