fix(form-core): Type mixin props as PropertyDeclarations (fixes: #1768)

[riovir]

What I did

1. Exposed the PropertyDeclarations from lit through @lion/core
2. Used the PropertyDeclarations in the form-core package mixins: strictly speaking the [FormControlMixin] Type error when extending with extra property #1768 issue is only concerned with the FormControlMixin. That said, updated the other mixins in the form-core for consistency's sake.

These changes should prevent type errors experienced by devs who extend form-related components with additional properties.

[changeset-bot]

🦋 Changeset detected

Latest commit: 93ef266

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@lion/core	Patch
@lion/form-core	Patch

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[gerjanvangeest]

Hi @riovir, thanks for the PR, sorry i didn't review it faster.
Could you rebase the changes, then i will approve it.

[gerjanvangeest]

This PR still needs some attention, maybe we can bring it back to live and finalise it soon!
Anybody lending a hand, feel free 💪!