Add log-format argument

[SergioGasquez]

Add -d/--defmt flag for monitor and flash subcommands.
Add -f/--log-format argument for monitor and flash subcommands.

cc @bugadani since you added this feature

Draft until properly tested. Did some testing and seems to be working fine!

We still need to figure out if we want opt-in or opt-out of defmt

[bugadani]

Since the framing should mostly be compatible with the classic string streams, I'd probably suggest this to be opt out instead of opt in. It's probably much more annoying to enable defmt constantly for those who want it, than to disable for the few who have some custom binary in their logs. Transmission errors might shade this a bit for those who use noisy UART still, so I'm not sure.

If you end up going down the opt-in road, maybe it wouldn't be the worst idea to future proof it a bit with --log-format=defmt, so that if new formats (or new defmt versions!) appear, this doesn't have to be broken.

[SergioGasquez]

To be honest, I don't have a preference if it should be opt-in or opt-out, any suggestion @esp-rs/espressif?

[bugadani]

As an idea, maybe we could enable printing location info with --log-format=defmt-verbose or similar option, so I think I shall update my opinion and vote for that format :)

[MabezDev]

I think with the --log-format change we're ready to go. I much prefer this to have to build a whole different espflash, and we can support other formats in the future.

Just one comment about making serial the default :)

[jessebraham]

LGTM

[bugadani]

I'm not sure why I didn't notice this but this isn't correct. The defmt parser is stateful, we can't just create a new one every time we have read some bytes.