sensor_msgs/Temperature and multi-channel readers

[J-C-Haley]

Added a sensor_msgs/Temperature topic, giving published temperatures a timestamp. Prior float64 is preserved for now.

Added channel parameter to phidgets_temperature, allowing for multi-port readers.

[mintar]

Thanks! One of the checks is failing. This is because I added a check yesterday to ensure that the code formatting complies with clang-format. To fix this, follow the pre-commit Formatting Checks section of the README. If you run pre-commit run -a, it should fix the formatting automatically for you. Once you commit that, the check should pass.

[mintar]

Thanks again for the PR. I've just reviewed it, and I think we should handle multiple channels the same way that they are handled in the other phidgets (for example, you can use the digital_output files as a template, reusing as much code as possible): One temperature class per channel, then one temperatures class to group all channels.