feat: add X-LaunchDarkly-Instance-Id header to server SDK (SDK-2353) … #2896

Job	Run time
build-test	6m 11s
contract-tests	3m 27s
contract-tests-curl	3m 30s
build-test-client-mac-curl	3m 56s
build-test-curl	6m 30s
build-test-client-mac	4m 55s
build-test-client-windows-curl	16m 15s
build-test-client-windows	13m 57s
	58m 41s

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