[php 8.3] Add json_validate rule

[TomasVotruba]

$json = '{"key": "value"}';
-if (json_decode($json, true) !== null && json_last_error() === JSON_ERROR_NONE) {
+if (json_validate($json)) {
    echo "Valid JSON";
}

[samsonasik]

json_validate seems has flags parameter, the change seems documented at https://php.watch/versions/8.3/json_validate for the transformation needs.

[samsonasik]

Downgrade first rule ready at:

• https://github.com/rectorphp/rector-downgrade-php/pull/313

[samsonasik]

implemented at PR

• https://github.com/rectorphp/rector-src/pull/7213