[WIP] Allow looping uart streamed gcode #767

Job	Run time
tests (ubuntu-latest, tests)	28s
build (ubuntu-latest, noradio)	1m 57s
tests (macos-latest, tests)	34s
build (ubuntu-latest, wifi)	2m 14s
tests (windows-latest, tests_nosan)	1m 25s
build (ubuntu-latest, bt)	2m 12s
build (macos-latest, noradio)	1m 36s
build (macos-latest, wifi)	1m 37s
build (macos-latest, bt)	1m 47s
build (windows-latest, noradio)	5m 27s
build (windows-latest, wifi)	6m 32s
build (windows-latest, bt)	4m 48s
	30m 37s

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