Improve the bot loading performance

[boydc2014]

Describe the bug

Composer is taking too much time to load a big bot. For example, in Calendar bot, it's taking up to 30-60s to see the first screen.

Version

Lastest main

Browser

• Electron distribution
• Chrome
• Safari
• Firefox
• Edge

OS

• macOS
• Windows
• Ubuntu

To Reproduce

Steps to reproduce the behavior:

1. open a big bot
2. wait the design page to show up

Expected behavior

Expect the first screen will show up very soon, within a few second, even the bot is considered as big.

Additional context

We had a proposal for hot/cold splitting which we can leverage the idea to break down the processing when loading.

[hibrenda]

addressed in #5853