Decompose complicated go-style reusable into composite actions

See this todo: https://github.com/knative/actions/blob/19bb67f8d7a618f796abf3ef6c7bc9dfc26234b9/.github/workflows/reusable-style.yaml#L71-L72

We currently have a `[reusable-helper-go-style.yaml](https://github.com/knative/actions/blob/main/.github/workflows/reusable-helper-go-style.yaml)` that should really be decomposed down in to composite actions. An example `gofmt` one already exists [here](https://github.com/knative/actions/tree/main/composite/style/gofmt).

While doing this, one could take a look at https://github.com/knative/actions/issues/65 and see what things we can improve on.

Start with .github/workflows/reusable-style.yaml at the linked TODO and compare .github/workflows/reusable-helper-go-style.yaml with the existing composite/style/gofmt example. Read issue 65 for possible improvements before defining the decomposition. Done means the go-style reusable workflow is decomposed into composite actions and the relevant workflow behavior is preserved.

Written by the indexing model from the issue text.