Refactor test covering dns_ede API

Refactor test covering dns_ede API

Migrate tests cases in client_test code which were exclusively testing
code which is now all wrapped inside ede compilation unit. Those are
testing maximum number of EDE, duplicate EDE as well as truncation of
text of an EDE.

Also add coverage for the copy of EDE from an edectx to another one, as
well as checking the assertion of the maximum EDE info code which can be
used.

(cherry picked from commit f9f41190b397429b151e48dac369ab5797ed6082)