MM-52532: Fix golangci warnings (#23709)

https://mattermost.atlassian.net/browse/MM-52532

- Replace golint with revive
- Add makezero linter
- Fix all the required linter failures

Some issues in enterprise and public modules
are yet to be fixed. We send this to expediate things.

server/channels/store/localcachelayer/terms_of_service_layer.go

@@ -47,7 +47,7 @@ func (s LocalCacheTermsOfServiceStore) Save(termsOfService *model.TermsOfService
 
 func (s LocalCacheTermsOfServiceStore) GetLatest(allowFromCache bool) (*model.TermsOfService, error) {
 	if allowFromCache {
-		if len, err := s.rootStore.termsOfServiceCache.Len(); err == nil && len != 0 {
+		if l, err := s.rootStore.termsOfServiceCache.Len(); err == nil && l != 0 {
 			var cacheItem *model.TermsOfService
 			if err := s.rootStore.doStandardReadCache(s.rootStore.termsOfServiceCache, LatestKey, &cacheItem); err == nil {
 				return cacheItem, nil