Extracting i18n functionality to i18n core library (#16914)

* extracting i18n functionality to i18n core library

* Removing utils.T

* Adding documentation and changing one function name for better explanation

* Changing other missing utils.T

* Adding license string

* Renaming corelibs to pkg

* Renaming corelibs to pkg (moving directory)

* Renaming from pkg to shared

* Fixing bodyPage.Html casing

* Fixing merges

* Fixing merge problem

* Fixing tests

app/bot.go

@@ -13,8 +13,8 @@ import (
 
 	"github.com/mattermost/mattermost-server/v5/mlog"
 	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v5/shared/i18n"
 	"github.com/mattermost/mattermost-server/v5/store"
-	"github.com/mattermost/mattermost-server/v5/utils"
 )
 
 // CreateBot creates the given bot and corresponding user.
@@ -72,7 +72,7 @@ func (a *App) CreateBot(bot *model.Bot) (*model.Bot, *model.AppError) {
 			return nil, err
 		}
 
-		T := utils.GetUserTranslations(ownerUser.Locale)
+		T := i18n.GetUserTranslations(ownerUser.Locale)
 		botAddPost := &model.Post{
 			Type:      model.POST_ADD_BOT_TEAMS_CHANNELS,
 			UserId:    savedBot.UserId,
@@ -471,7 +471,7 @@ func (a *App) getDisableBotSysadminMessage(user *model.User, userBots model.BotL
 		botList += fmt.Sprintf("* %v\n", bot.Username)
 	}
 
-	T := utils.GetUserTranslations(user.Locale)
+	T := i18n.GetUserTranslations(user.Locale)
 	message = T("app.bot.get_disable_bot_sysadmin_message",
 		map[string]interface{}{
 			"UserName":           user.Username,