Add support for the ESP32-H2

[jessebraham]

This was thankfully a pretty straight-forward process, but there are some rough edges in this PR I'd like to point out:

• I had to move esp-backtrace and esp-println to [dependencies], as we're not able to feature-gate dev dependencies.
• To avoid needing to change .cargo/config.toml when switching chip, I've just generated empty linker scripts for two of the three files on the H2; this is a little hacky, so I'm open to suggestions for better solutions, but it does work.
• I've changed the channels in all examples to 15; I kept forgetting to change them when I'd switch branches as stuff, makes sense to just keep them all the same to me. If there's any reason not to do this (or if we should use a different channel) please let me know.

I've tested all combination of examples/chips with success:

	receive_all_frames	receive_frame	send_broadcast_frame	send_frame
ESP32-C6 -> ESP32-C6	✅ (C6)	✅ (C6)	✅ (C6)	✅ (C6)
ESP32-C6 -> ESP32-H2	✅ (H2)	✅ (H2)	✅ (C6)	✅ (C6)
ESP32-H2 -> ESP32-C6	✅ (C6)	✅ (C6)	✅ (H2)	✅ (H2)
ESP32-H2 -> ESP32-H2	✅ (H2)	✅ (H2)	✅ (H2)	✅ (H2)

I did have some strange issues while testing, which ultimately resolved themselves, so it wouldn't hurt to do another round.

As I've already mentioned to you, once this PR is merged I'll have a follow-up doing some refactoring/cleanup.

[bjoernQ]

LGTM - also verified with a TI CC2531 sniffer