[make:validator] Add --target option that allows restricting automatically where the constraint class can be used

[nxtpge]

Q	A
Branch?	1.x
Bug fix?	no
New feature?	yes
Deprecations?	no
Issues
License	MIT

This pull request adds the --target option to the make:validator command to speed up the creation and the use of a custom validation constraint.

Usage

php bin/console make:validator FooValidator --target=class
php bin/console make:validator FooValidator --target=method
php bin/console make:validator FooValidator --target=property

Result

Target	Constraint class changes
class	- Add the #[\Attribute(\Attribute::IS_REPEATABLE)] declaration, - Add the Constraint::getTargets required method.
method	- Add the #[\Attribute(\Attribute::TARGET_METHOD | \Attribute::IS_REPEATABLE)] declaration.
property	- Add the #[\Attribute(\Attribute::TARGET_PROPERTY | \Attribute::IS_REPEATABLE)] declaration.