Add metadata retrieved from the `context` to the user agent when a new HTTP client is created #5089

Job	Run time
run-determination	1s
check-license-headers (./)	18s
build (internal/arduino/discovery/discovery_client)	13s
check-config (./)	10s
build (rpc/internal/client_example)	26s
build (commands/term_example)	32s
check-formatting (./)	7s
check-outdated (./)	10s
check-style (./)	52s
	2m 49s

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