Add support for GPIO Expanders

[Fortinbra]

Adding support for the PCA9535 16bit GPIO expander from Texas Instruments https://www.ti.com/document-viewer/PCA9535/datasheet/GUID-2E758BF2-C717-41D1-BC2E-80CE2E71C3C9

This will allow us to expand the number of digital pins by 16 per each expander added to the I²C bus.

[schnoog]

Would be great if also MCP23017 support could be integrated. These I2C port expanders include (switchable) pull up resistors.

[n-i-x]

Initial PoC is at https://github.com/n-i-x/GP2040-CE/tree/i2c_expander

It supports PCA95xx expanders currently.

The branch needs to be updated to the new protobuf to continue progress.

Initial latency testing shows no major impact to latency.

TODO:

• Update branch to protobuf and migrate settings to it
• Convert pca object to a more generic expander interface to allow for additional expander types/protocols
• Support multiple expanders
• Support keyboard input (requires modifying the keyboard addon)
• Move addon init code out of this branch and into a more generic PR (I think there is another task for this)
• (long term) support operating on the same i2c bus as OLED displays

[TheTrainGoes]

This work has been completed via #1025