Allow for overriding TwoWire class's internal functions

[Dan-Kouba]

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Problem

The current implementation of the TwoWire class does not define its methods as virtual, therefore preventing any classes that inherit from TwoWire from overriding those functions.

Solution

This PR adds the virtual identifier to most internal functions allowing for override when deriving from this class.

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Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)

[eberseth]

Perhaps make the I2C interface protected in the class as well

protected:
  hal_i2c_interface_t _i2c;

cc @avtolstoy

[Dan-Kouba]

@eberseth I'm good with that — would preclude the interface() function from being needed in derived classes. Shall I submit a new commit?

[eberseth]

@eberseth I'm good with that — would preclude the interface() function from being needed in derived classes. Shall I submit a new commit?

You can make changes, squash, and force push to overwrite the branch.