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/app/platform/log.go

@@ -141,7 +141,7 @@ func (ps *PlatformService) GetLogsSkipSend(page, perPage int, logFilter *model.L
 		var lineCount int
 		const searchPos = -1
 		b := make([]byte, 1)
-		var endOffset int64 = 0
+		var endOffset int64
 
 		// if the file exists and it's last byte is '\n' - skip it
 		var stat os.FileInfo

server/channels/app/platform/web_hub.go

@@ -442,7 +442,7 @@ func (h *Hub) Start() {
 					})
 					continue
 				}
-				var latestActivity int64 = 0
+				var latestActivity int64
 				for _, conn := range conns {
 					if !conn.active {
 						continue