Feature/serial command improvements #256

Job	Run time
build-captive-portal	54s
get-targets / generate-matrix	9s
build-firmware (Wemos-D1-Mini-ESP32)	2m 4s
build-firmware (Wemos-Lolin-S2-Mini)	2m 2s
build-firmware (Wemos-Lolin-S3)	2m 23s
build-firmware (Pishock-2023)	1m 59s
build-firmware (Pishock-Lite-2021)	2m 10s
build-firmware (Seeed-Xiao-ESP32S3)	2m 1s
build-filesystem	54s
merge-images (Wemos-D1-Mini-ESP32)	32s
merge-images (Wemos-Lolin-S2-Mini)	26s
merge-images (Wemos-Lolin-S3)	31s
merge-images (Pishock-2023)	28s
merge-images (Pishock-Lite-2021)	36s
merge-images (Seeed-Xiao-ESP32S3)	23s
done	1s
	17m 33s

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