fix(mock): update gomock import path for build compatibility

[dd-rK]

Problem

The make build and make test commands fail due to inconsistent gomock imports:

• mockgen generates code that imports go.uber.org/mock/gomock
• Several test files still import github.com/golang/mock/gomock

This results in type mismatch errors like:
cannot use mockCtrl (type *github.com/golang/mock/gomock.Controller) as *go.uber.org/mock/gomock.Controller

Solution

• Updated all gomock imports to use go.uber.org/mock/gomock
• Added troubleshooting instructions to the README for future contributors

Impact

• Build and tests now succeed consistently
• Makes it easier for new contributors to get started with local development

[dd-rK]

Hi maintainers 👋,

This PR addresses the build inconsistency caused by mismatched gomock import paths. The generated mocks reference go.uber.org/mock/gomock, while several test files still used github.com/golang/mock/gomock, leading to test failures.

✅ Aligned all references to use go.uber.org/mock/gomock, matching the generated mocks
🛠️ Verified that make build and make test now pass locally
📘 Added troubleshooting notes to the README to help future contributors

Let me know if you'd like this broken into smaller commits or adjusted in any way. Thanks for reviewing and maintaining this project!

– @dd-rK

[dd-rK]

@andresrcs @adrianlzt 🙏 for a quick review when you get a chance.