feat: add operations rest client to support long-running operations. (#311)

* feat: add operations rest client to support long-running operations.

* fix: address test coverage gaps in operations rest client.

* fix: removed stray print statement.

* fix: address lint, blacken, and mypy issues.

* fix: address pytype, more coverage issues

* fix: addressed additional pytype issues and one coverage line.

* fix: renamed OperationsRestClient to AbstractOperationsClient.

Co-authored-by: Kenneth Bandes <kbandes@google.com>
7 files changed