use enum to return precise FIFO state

[2bndy5]

I got this idea from developing rf24-rs project.

This has the advantage of accurately describing a FIFO's state (including data corruption over SPI) when using RF24::isFifo().

I also deprecated the overloaded RF24::isFifo(bool about_tx, bool check_empty) because the data returned could be considered inaccurate.

[github-actions]

Memory usage change @ fd90bc4

Board	flash	%	RAM for global variables	%
arduino:avr:nano	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrzero	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0

Click for full report table

Board	examples/GettingStarted flash	%	examples/GettingStarted RAM for global variables	%	examples/AcknowledgementPayloads flash	%	examples/AcknowledgementPayloads RAM for global variables	%	examples/ManualAcknowledgements flash	%	examples/ManualAcknowledgements RAM for global variables	%	examples/StreamingData flash	%	examples/StreamingData RAM for global variables	%	examples/MulticeiverDemo flash	%	examples/MulticeiverDemo RAM for global variables	%	examples/InterruptConfigure flash	%	examples/InterruptConfigure RAM for global variables	%	examples/scanner flash	%	examples/scanner RAM for global variables	%	examples/encodeRadioDetails flash	%	examples/encodeRadioDetails RAM for global variables	%
arduino:avr:nano	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0
arduino:samd:mkrzero	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0

Click for full report CSV

Board,examples/GettingStarted<br>flash,%,examples/GettingStarted<br>RAM for global variables,%,examples/AcknowledgementPayloads<br>flash,%,examples/AcknowledgementPayloads<br>RAM for global variables,%,examples/ManualAcknowledgements<br>flash,%,examples/ManualAcknowledgements<br>RAM for global variables,%,examples/StreamingData<br>flash,%,examples/StreamingData<br>RAM for global variables,%,examples/MulticeiverDemo<br>flash,%,examples/MulticeiverDemo<br>RAM for global variables,%,examples/InterruptConfigure<br>flash,%,examples/InterruptConfigure<br>RAM for global variables,%,examples/scanner<br>flash,%,examples/scanner<br>RAM for global variables,%,examples/encodeRadioDetails<br>flash,%,examples/encodeRadioDetails<br>RAM for global variables,%
arduino:avr:nano,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0
arduino:samd:mkrzero,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0

[2bndy5]

works fine with the py wrapper:

>>> from RF24 import RF24
>>> r = RF24(22, 0)
>>> r.begin()
True
>>> r.isFifo(1)
RF24.rf24_fifo_state_e.RF24_FIFO_EMPTY
>>> r.enableAckPayload()
>>> r.writeAckPayload(1, b"bla")
True
>>> r.isFifo(1)
RF24.rf24_fifo_state_e.RF24_FIFO_OCCUPIED
>>> r.writeAckPayload(1, b"bla")
True
>>> r.writeAckPayload(1, b"bla")
True
>>> r.writeAckPayload(1, b"bla")
False
>>> r.isFifo(1)
RF24.rf24_fifo_state_e.RF24_FIFO_FULL
>>> r.flush_tx()
15
>>> r.isFifo(1)
RF24.rf24_fifo_state_e.RF24_FIFO_EMPTY