tests: thrift: hello: potentially move to samples

[Chris Friedt]

Right now, all that the test does is run, but it's missing some key ztest checks in the form of zassert checks.

For example, a global variable could be used to ensure that the ping was successful (zassert_true()). Similarly, a global variable could be used to store the echo message (zassert_mem_equal()). Lastly, if the counter were a global variable, then it could be checked with the local counter variable (zassert_equal()).

ping
echo: Hello, world!
counter: 1
counter: 2
counter: 3
counter: 4
counter: 5