Refactor airnode-examples to use default contract functionality from airnode-node #1838
Description
Functions in airnode-examples like getAirnodeRrpAddress and getExistingAirnodeRrpV0 were written before airnode-node was capable of defaulting to deployed contract addresses (implemented in #1755 and #1814). Consequently, it would be better to leverage this airnode-node functionality rather than have it partially duplicated in airnode-examples. See also this comment and the original comment inspiring this by @bdrhn9.