fix(core): UID doesn't exist on the component public instance in Vue 3 #1090

[Florent-Bouisset]

Summary

fixes #1090

uid is not on the ComponentPublicInstance but on the ComponentInternalInstance on vue3

we can do as before by accessing the internal instance with instance.$.uid

    const uid = instance?.$?.uid || instance._uid
    $registerAs = `_vuelidate_${uid}`

but accessing internal instance is not recommended, I suggest to create our own uid instead.
The vuelidate uid doesn't need to be same as the vue uid right ?

Metadata

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• I have read the Contribution Guides
• It's submitted to the next branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/vuelidate/vuelidate/blob/master/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

[dobromir-hristov]

I think the UID is not necessary to be the same, but I hope it wont intervene with entire components being rendered on/off.