Add support for client certificate and private key #1367

Job	Run time
compile-examples (arduino:mbed:nicla_vision, nicla_vision)	15m 28s
compile-examples (arduino:mbed:envie_m7, envie_m7)	25m 46s
compile-examples (arduino:mbed:nano33ble, nano33ble)	7m 1s
compile-examples (arduino:mbed:nicla_voice, nicla_voice)	4m 55s
compile-examples (arduino:mbed:edge_control, edge_control)	4m 57s
compile-examples (arduino:mbed:envie_m7:target_core=cm4, envie_m7_core_cm4)	5m 2s
compile-examples (arduino:mbed:nanorp2040connect, nanorp2040connect)	11m 45s
compile-examples (arduino:mbed:giga, giga)	24m 21s
compile-examples (arduino:mbed:nicla_sense, nicla_sense)	11m 23s
compile-examples (arduino:mbed:opta, opta)	17m 27s
	2h 8m 5s

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