revert available() algorithm (#914) #413

Job	Run time
check_formatting / cpp_linter	7s
build (adafruit_feather_rp2040) / build	2m 11s
build (arduino_nano_rp2040_connect) / build	2m 18s
build (adafruit_itsybitsy_rp2040) / build	1m 44s
build (adafruit_qtpy_rp2040) / build	2m 24s
build (pico) / build	1m 57s
build (pimoroni_pga2040) / build	1m 47s
build (pimoroni_picolipo_4mb) / build	2m 25s
build (pimoroni_picolipo_16mb) / build	4m 5s
build (pimoroni_tiny2040) / build	2m 29s
build (sparkfun_micromod) / build	1m 40s
build (sparkfun_promicro) / build	2m 4s
build (sparkfun_thingplus) / build	1m 39s
	26m 50s

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