[LR11x0] Expose instantaneous RSSI measurement

[GUVWAF]

The function getRssiInst() is used for the LR11x0 to get an instantaneous RSSI measurement, but it is protected. This exposes it by overloading getRSSI() with the bool packet parameter added just like is done for SX127x, SX126x, SX128x and LR2021.

I also rephrased Recorded Signal Strength Indicator to Received Signal Strength Indicator as I believe that's the more common term.

[jgromes]

Thanks for the contribution! In testing, does this return the some reasonable numbers? I am asking because on the other devices (most recently on LR2021), I had to make sure Rx mode was active, otherwise the return value was stuck at -128 dBm.

[GUVWAF]

Yes, I get reasonable numbers, but indeed I just checked that's only when we're in receive mode. Do you want me to add the bool skipReceive parameter just like for LR2021 and let it go to receive mode if that value is false?

[jgromes]

I think that would be the best option, that way we will keep the same interface for all the LoRa modules.

[GUVWAF]

Added in the latest commit, following the same approach as the LR2021.
I also slightly adjusted the description for this parameter for the LR2021.

[jgromes]

Looking good now - merged, thank you for the contribution!