Don't call Action while ComputedValue is computing

[MoonBall]

Warn when calling action while ComputedValue is computing. This PR is related to #2346.

Code change checklist

• Added/updated unit tests
• Updated changelog
• Updated /docs. For new functionality, at least API.md should be updated
• Verified that there is no significant performance drop (npm run perf)

[gitpod-io]

[mweststrate]

In general, it is not forbidden to call actions from computed values in MobX, although there are tricky edge cases, the tricks people pull otherwise to avoid the limitation are even worse. Thanks for the attempt though!

[MoonBall]

Thank you for your explanation. I learn more after I understand the sentence "anything done in an action will not be tracked by the computed" you said.