MM-45195: Use api4/bot and app/bot to use logger context (#20729)

https://mattermost.atlassian.net/browse/MM-45195

```release-note
NONE
```

app/post.go

@@ -46,7 +46,7 @@ func (s *postServiceWrapper) CreatePost(ctx *request.Context, post *model.Post)
 	return s.app.CreatePostMissingChannel(ctx, post, true)
 }
 
-func (a *App) CreatePostAsUser(c *request.Context, post *model.Post, currentSessionId string, setOnline bool) (*model.Post, *model.AppError) {
+func (a *App) CreatePostAsUser(c request.CTX, post *model.Post, currentSessionId string, setOnline bool) (*model.Post, *model.AppError) {
 	// Check that channel has not been deleted
 	channel, errCh := a.Srv().Store.Channel().Get(post.ChannelId, true)
 	if errCh != nil {
@@ -83,7 +83,7 @@ func (a *App) CreatePostAsUser(c *request.Context, post *model.Post, currentSess
 	isCRTReply := post.RootId != "" && a.IsCRTEnabledForUser(c, post.UserId)
 	if !fromWebhook && !fromBot && !isCRTReply {
 		if _, err := a.MarkChannelsAsViewed(c, []string{post.ChannelId}, post.UserId, currentSessionId, true); err != nil {
-			mlog.Warn(
+			c.Logger().Warn(
 				"Encountered error updating last viewed",
 				mlog.String("channel_id", post.ChannelId),
 				mlog.String("user_id", post.UserId),