WebCrypto: Add test for deriving a KDF key using ECDH (#48852)
Check that the correct key is derived when using ECDH to derive an HKDF
or PBKDF2 key.
This test has been ported from WebKit's source [1], defined to check the
impact of the 'Get Key Length' behavior of HKDF and PBKDF2, which should
return 'null' in both cases, in the 'deriveKey' operation.