Code cleanup (#9992)

* Value assigned to a variable is never read before being overwritten

* The result of append is not used anywhere

* Suspicious assignment of range-loop vars detected

* Unused method receiver detected

* Revert "Auxiliary commit to revert individual files from 54edcb445484a2e5d79612e19af8e949b8861253"

This reverts commit bbd1e1beabf7b0c5cfc4f514dcc820062ad6c063.

* Method modifies receiver

* Fix test

* Duplicate imports detected

* Incorrectly formatted error string

* Types of function parameters can be combined

* One more "Unused method receiver detected"

* Unused parameter detected in function

runtime/service_registry_test.go

@@ -16,10 +16,10 @@ type secondMockService struct {
 	status error
 }
 
-func (m *mockService) Start() {
+func (_ *mockService) Start() {
 }
 
-func (m *mockService) Stop() error {
+func (_ *mockService) Stop() error {
 	return nil
 }
 
@@ -27,10 +27,10 @@ func (m *mockService) Status() error {
 	return m.status
 }
 
-func (s *secondMockService) Start() {
+func (_ *secondMockService) Start() {
 }
 
-func (s *secondMockService) Stop() error {
+func (_ *secondMockService) Stop() error {
 	return nil
 }