REST API: Make JSON Schema enum more robust for non-string types

[TimothyBlynJacobs]

The enum JSON schema keyword allows for enforcing that the provided value is one of the listed values. This can be used with any type of value. Our implementation, however, doesn't apply the same type coercion when doing regular validation.

In other words, for an enum of [ 0, 1 ] I should be able to pass "1".

To do this, I think we might want to move the enum validation to the end of rest_validate_value_from_schema so that type validation has already been applied, and then either call rest_sanitize_value_from_schema before passing the value to the enum check, or just do the type casting.

We'll also need to pay special care to arrays/objects applying rest_stabilize_value and making sure that the type safe in_array() check has the correct JSON semantics.

Added support for type coercion in enum JSON Schema keyword.

Trac ticket: https://core.trac.wordpress.org/ticket/51911

[TimothyBlynJacobs]

In 50010:

REST API: Support type coercion when validating the enum JSON Schema keyword.

Previously, the enum keyword was validated by perform a strict equality check. For string types this is generally ok, but it prevented using alternative types like number when rich type support isn't available.

Now the same level of type coercion/sanitization is applied when validating enum as all other validation checks. This means that a value of "1" will be accepted for an enum of [ 0, 1 ]. Additionally, object types now properly ignore key order when checking for equality.

Props yakimun.
Fixes #51911.

Merged in ​https://github.com/WordPress/wordpress-develop/commit/0ceee0f871ac442f38e871b889eb6b77b611b487. Thanks for your great work on this @yakimun!