Privatize EADItem details, increase label range to i16 #288

Job	Run time
check-style	19s
unit-tests (hacspec, hacspec, ead-none)	1m 6s
unit-tests (hacspec, hacspec, ead-zeroconf)	1m 8s
unit-tests (hacspec, psa, ead-none)	1m 13s
unit-tests (hacspec, psa, ead-zeroconf)	1m 50s
unit-tests (rust, psa, ead-none)	1m 21s
unit-tests (rust, psa, ead-zeroconf)	1m 3s
build-coap-example	0s
build-edhoc-package	0s
build-example-for-cortex-m4	0s
build-static-lib-and-headers	0s
hacspec-to-fstar	0s
run-example-on-qemu	0s
release	0s
	8m 0s

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