Add wifi.radio.tx_power

[todbot]

Resolves #6540

[jepler]

@todbot I revised the initial comment on this PR using the special syntax for closing an issue when a PR is accepted.

[todbot]

Thanks!

[askpatrickw]

I actually started to work on this myself, and the get, set in Radio.c made sense. I also thought tx_power would need to go in ports/espressif/common-hal/wifi/Radio.h, is that not the case?

I had no idea shared-bindings would need updating, so I'm glad you took this on, ty!

[todbot]

I was also confused by no function decls in ports/espressif/common-hal/wifi/Radio.h. I think the rationale is that shared-bindings contains the C API headers and the individual ports' headers contain only platform-specific stuff. So, the Radio.h in shared-bindings is the header for every implementation of wifi.radio.

And apologies for stepping on your work on this! And thanks for the extra set of eyes. I'm always nervous about touching this repo publicly. :)

[askpatrickw]

You didn't step on me... I don't know C so it would have been a steep learning curve.
I'll test this later tonight or tomorrow during the Deep Dive window.

Thank you again!

[dhalbert]

Thanks! One doc clarification requested.

[tannewt]

I was also confused by no function decls in ports/espressif/common-hal/wifi/Radio.h. I think the rationale is that shared-bindings contains the C API headers and the individual ports' headers contain only platform-specific stuff. So, the Radio.h in shared-bindings is the header for every implementation of wifi.radio.

This is exactly right. Another way to think about it is that the shared-bindings header declares all of the functions used by the shared-bindings implementation.

[dhalbert]

Thanks! Ready to merge when build is done.