[workflow] Standardize workflow blocking and nonblocking APIs

[suquark]

Why are these changes needed?

This PR unified the semantics of some workflow APIs.

Those workflow APIs acts on workflow tasks so they could be blocked for a long time. So we have both the blocking and non-blocking versions for them: xxx for blocking and xxx_async for non-blocking APIs.

Checks

• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(