Add alias board.STEMMA_I2C for all boards with qwiic/stemma/QT

[Neradoc]

This aliases board.I2C and board.STEMMA_I2C on all boards where they are on the same pins. Meaning they both return the same singleton object. I went through the whole list on circuitpython.org, hopefully I didn't make too many mistakes.
I'm a little worried it might be confusing though. Documentation and guides will have to clarify when I2Cand STEMMA_I2C are the same and when they are not.
Note that one sparkfun board already also had a board.QWIIC alias.
Final step for #4638 ?

[dhalbert]

@kattni What do you think about whether board.STEMMA_I2C should exist on boards where board.I2C and board.STEMMA_I2C are the same?

[dhalbert]

@kattni What do you think about whether board.STEMMA_I2C should exist on boards where board.I2C and board.STEMMA_I2C are the same?

@ladyada: same q for you.

[kattni]

@dhalbert I want to see this happen. Consistency is important, and if we have it on the boards that use SCL1/SDA1, I think having it on all boards would work. We can document that it's an alias if that is desired, but I would love to see this across all boards.

[dhalbert]

Thank you for doing this extensive inventory!

[dhalbert]

@dhalbert I want to see this happen. Consistency is important, and if we have it on the boards that use SCL1/SDA1, I think having it on all boards would work. We can document that it's an alias if that is desired, but I would love to see this across all boards.

OK, sounds good! I was not sure if there were hidden considerations. It will certainly make Learn Guide code easier. @ladyada -- I will not wait for your reply.

[ladyada]

yes please have it point to the same if they're the same!