Ability to pause/resume consumer

**Is your feature request related to a problem? Please describe.**
Under certain conditions (say in flow control mode), I would like to pause the consumer. I see this feature already supported for JAVA client. https://pulsar.apache.org/api/client/2.7.0-SNAPSHOT/

**Describe the solution you'd like**
Like JAVA client, I would like Golang client to support pause/resume feature for consumers.

**Describe alternatives you've considered**
None. Looking for some suggestions from the community.

**Additional context**

Start by comparing the Go consumer API with the Java client API linked in the issue, focusing on how pause and resume interact with flow-control mode. No Go files or tests are named; done requires agreed semantics, an exposed Go API, implementation, and tests covering both operations.

Written by the indexing model from the issue text.