Avoid circular dependencies in @grpc/grpc-js

### Is your feature request related to a problem? Please describe.

While Node.js supports circular dependencies, it comes with some drawbacks and in my experiences it is best to avoid them. As an example, tree shaking with Rollup becomes less effective.

### Describe the solution you'd like

Could we refactor the code in such a way, that there are no import cycles?

### Describe alternatives you've considered

-

### Additional context

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