[WIP][Form] Add TelType

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | https://github.com/symfony/symfony/issues/8026
| License       | MIT
| Doc PR        | https://github.com/symfony/symfony-docs/pull/4040
This should not be a view transformer but a model transformer. The parent type (``text``) expects the norm data to be string, so it should be respected in this type