- Fixes support for the same address being present more than once in the
address list, which was accidentally broken in #34244.
- Change the call attribute to encode the hash as an integer instead of
a string.

See grpc/proposal#475 for details.

While I was at it, I greatly simplified the logic, avoiding an unnecessary duplicate loop over all endpoints that we didn't need to be doing.

I removed an unnecessary end2end test that was broken by this change.  That test actually should have broken when I first changed ring_hash to delegate to pick_first back in #34244, and I'm not sure why it didn't.  But it definitely broke here when I changed the logic to not choose endpoints in any specific order when triggering connection attempts, and since the test was really intended to test a behavior that we no longer guarantee, I removed it.

In its place, I added a unit test that shows the new behavior in a much clearer way.  (Originally, we didn't have a good way to write unit tests for LB policies, so all of our tests were written as e2e tests.  Now that we do have a good framework for unit tests, we've been slowly finding e2e tests that really should be unit tests instead, and moving them over when we find them.)

Closes #38741

COPYBARA_INTEGRATE_REVIEW=#38741 from markdroth:ring_hash_tf_and_connecting_fix 6c4c773
PiperOrigin-RevId: 728255272

See grpc/proposal#475 for details.

While I was at it, I greatly simplified the logic, avoiding an unnecessary duplicate loop over all endpoints that we didn't need to be doing.

I removed an unnecessary end2end test that was broken by this change.  That test actually should have broken when I first changed ring_hash to delegate to pick_first back in grpc#34244, and I'm not sure why it didn't.  But it definitely broke here when I changed the logic to not choose endpoints in any specific order when triggering connection attempts, and since the test was really intended to test a behavior that we no longer guarantee, I removed it.

In its place, I added a unit test that shows the new behavior in a much clearer way.  (Originally, we didn't have a good way to write unit tests for LB policies, so all of our tests were written as e2e tests.  Now that we do have a good framework for unit tests, we've been slowly finding e2e tests that really should be unit tests instead, and moving them over when we find them.)

Closes grpc#38741

COPYBARA_INTEGRATE_REVIEW=grpc#38741 from markdroth:ring_hash_tf_and_connecting_fix 6c4c773
PiperOrigin-RevId: 728255272