fix(vue3): prevent mixin leakage caused by inspection, fix #2037

[lehni]

Description

See #2037 for description. I have tested this on Chrome and it works as expected.

Additional context

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).

[lehni]

@himself65 I've accepted your change. CircleCI fails, I don't understand why.

[niksy]

What can we do to get this merged?

[lehni]

@yyx990803 pinging you again on this. This is save to merge, and it's a pretty bad bug, see https://github.com/vuejs/devtools/issues/2037

[liutkin]

Any ETA on this? This bug causes a huge mess in the large Vue app when global mixin is involved and computed keys being leaked into child components.