[WIP] Allow looping uart streamed gcode #765

Job	Run time
tests (ubuntu-latest, tests)	35s
build (ubuntu-latest, noradio)	1m 52s
tests (macos-latest, tests)	38s
build (ubuntu-latest, wifi)	2m 8s
tests (windows-latest, tests_nosan)	1m 32s
build (ubuntu-latest, bt)	2m 4s
build (macos-latest, noradio)	1m 36s
build (macos-latest, wifi)	2m 13s
build (macos-latest, bt)	2m 6s
build (windows-latest, noradio)	4m 30s
build (windows-latest, wifi)	5m 53s
build (windows-latest, bt)	5m 39s
	30m 46s

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