Deprecate interface Symfony\Component\Validator\PropertyMetadataInterface
minor #12715 Deprecate interface Symfony\Component\Validator\PropertyMetadataInterface (aferrandini)

This PR was merged into the 2.7 branch.

Discussion
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Deprecate interface Symfony\Component\Validator\PropertyMetadataInterface

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #12678
| License       | MIT

Deprecate interface Symfony\Component\Validator\PropertyMetadataInterface

Commits
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4b3f135 Deprecate interface Symfony\Component\Validator\PropertyMetadataInterface