fix(core): fix caching issue in CMS between studio and bp

[laurentlp]

This PR fixes an issue where overriding a bot inside the Bot Pipeline would not invalidate the CMS cache in the studio causing the UI not to display newly created content-elements.

Closes botpress/v12#1581

Closes DEV-2203

[linear]

DEV-2203 (BUG) Overriding a bot on a stage breaks DialogEngine and fails to update content-elements (botpress/botpress botpress/v12#1581)

Describe the bug
In a workspace with 3 pipeline stages when a bot on some stage is overridden (using on_request_change pipeline hook below):

1. Newly added contents are not visible in the flow editor and contents page of the bot
   
2. Chat stops working
   

May be related to this issue.

To Reproduce
Steps to reproduce the behavior:

1. Set up a pipeline with 3 stages
2. Create an empty bot
   
3. Add some initial content to it
   
4. Promote the bot to the next stage
   
5. Promoted bot should work for now
   
6. Add some new content to the original bot and promote it again
   
7. Open the studio for the promoted bot. You should see newly added content-elements rendered empty and webchat not working
   
   

Expected behavior
The promoted bot should have a working webchat and render newly added content-elements in the flow editor

Environment (please complete the following information):

• OS: macOS
• Browser Chrome
• Browser Version Version 96.0.4664.110 (Official Build) (x86_64)
• Botpress Version v12.26.7
• NodeJS v12.18.1

Additional context
Add any other context about the problem here.

botpress/borpress botpress/v12#1581 by @ daukadolt