feat(go): Simplify generated code

[amckinney]

This adapts generated endpoint structure to clean up the generated code and reduce repetition. This also proposes a simpler errorDecoder constructor, splits specific method invocations across multiple lines, and removes a variety of unnecessary newlines across the SDK.

Now, users are presented with an endpoint that looks something along the lines of the following:

func (c *Client) Get(
	ctx context.Context,
	id string,
	opts ...option.RequestOption,
) (string, error) {
	options := core.NewRequestOptions(opts...)
	baseURL := internal.ResolveBaseURL(
		options.BaseURL,
		c.baseURL,
		"https://api.foo.io/v1",
	)
	endpointURL := internal.EncodeURL(
		baseURL+"/%v",
		id,
	)
	headers := internal.MergeHeaders(
		c.header.Clone(),
		options.ToHeader(),
	)
	errorCodes := map[int]func() error{
		400: func(apiError *core.APIError) error {
			return &acme.UntypedError{
                         	APIError: apiError,
                         }
		},
		404: func(apiError *core.APIError) error {
			return &acme.NotFoundError{
                         	APIError: apiError,
                         }
		},
	}

	var response string
	if err := c.caller.Call(
		ctx,
		&internal.CallParams{
			URL:             endpointURL,
			Method:          http.MethodGet,
			MaxAttempts:     options.MaxAttempts,
			Headers:         headers,
			BodyProperties:  options.BodyProperties,
			QueryParameters: options.QueryParameters,
			Client:          options.HTTPClient,
			Response:        &response,
			ErrorDecoder:    internal.NewErrorDecoder(errorCodes),
		},
	); err != nil {
		return "", err
	}
	return response, nil
}

[github-actions]

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