remove dependency on mockgen executable

[PereRohit]

If mockgen is not installed on the users system, the process fails and the generated files are deleted. Maybe the user wants to use a different mocking framework or write their own mock code.

Let the generated files be as is and display a message for mocks not generated due to missing mockgen.

Can additionally add a flag --install-deps that can install dependencies like mockgen if not found.

[PereRohit]

mockgen integrates well with the existing go testing package and provides functions that are used for validation and/or mocking.
Instead of removing this, let's install the required mockgen before generating the mocks using go install

go install github.com/golang/mock/mockgen@v1.6.0