[Task][Go SDK][Cleanup]: Migrate passert package exclusively to the generic register package.

### What needs to happen?

The go generate lines would need to be removed:
https://github.com/apache/beam/blob/master/sdks/go/pkg/beam/testing/passert/passert.go#L31

and the registrations in `passert.shims.go` https://github.com/apache/beam/blob/master/sdks/go/pkg/beam/testing/passert/passert.shims.go should be moved to `init()` blocks using the register package instead.

Partially done in #27565, this will be easier to work on once prism is the default runner, since the error unregistered portions will be provided as test failures. See #24789

### Issue Priority

Priority: 3 (nice-to-have improvement)

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