refactor(stepper): rework buttons to handle Ivy (#15429)

[crisbeto]

Equivalent of #15429 for the Ivy branch.

In Ivy inheriting host bindings works correctly by merging the two declarations, whereas in ViewEngine the bindings aren't inherited at all. This means that with our current setup the click listener on the buttons will be invoked twice with Ivy.

These changes rework the buttons so that they work both with Ivy and ViewEngine.

[ngbot]

I see that you just added the pr: merge ready label, but the following checks are still failing:
     status "ci/circleci: api_golden_checks" is failing
     status "ci/circleci: bazel_build_test" is failing
     status "ci/circleci: build_release_packages" is failing
     status "ci/circleci: e2e_tests" is failing
     status "ci/circleci: lint" is failing
     status "ci/circleci: prerender_build" is failing
     status "ci/circleci: tests_browserstack" is failing
     status "ci/circleci: tests_local_browsers" is failing
     status "ci/circleci: tests_saucelabs" is failing
     missing required labels: target: *

If you want your PR to be merged, it has to pass all the CI checks.

If you can't get the PR to a green state due to flakes or broken master, please try rebasing to master and/or restarting the CI job. If that fails and you believe that the issue is not due to your change, please contact the caretaker and ask for help.

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}