Renamed `FQBN.Packager` -> `FQBN.Vendor` #5175

Job	Run time
run-determination	1s
check-config (./)	9s
check-license-headers (./)	13s
check-formatting (./)	7s
check-outdated (./)	8s
build (internal/arduino/discovery/discovery_client)	11s
check-style (./)	1m 6s
build (rpc/internal/client_example)	20s
build (commands/term_example)	21s
	2m 36s

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