[WIP] Allow looping uart streamed gcode #763

Job	Run time
tests (ubuntu-latest, tests)	35s
tests (macos-latest, tests)	41s
build (ubuntu-latest, noradio)	1m 57s
tests (windows-latest, tests_nosan)	1m 26s
build (ubuntu-latest, wifi)	2m 11s
build (ubuntu-latest, bt)	2m 10s
build (macos-latest, noradio)	2m 3s
build (macos-latest, wifi)	1m 49s
build (macos-latest, bt)	2m 10s
build (windows-latest, noradio)	5m 39s
build (windows-latest, wifi)	5m 20s
build (windows-latest, bt)	4m 39s
	30m 40s

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