Add CDATA_WRAPPING_NAME_PATTERN support to XmlEncoder

This PR introduces a new option for the Symfony Serializer component's XmlEncoder: CDATA_WRAPPING_NAME_PATTERN.

While Symfony already provides CDATA_WRAPPING_PATTERN to wrap field content in CDATA based on a regex match, this new feature enables CDATA wrapping based on the field name—regardless of the field's content.

Example use case:

$this->encoder->encode($data, 'xml', [
    XmlEncoder::CDATA_WRAPPING_NAME_PATTERN => '(firstname|lastname)'
]);

This ensures that fields named firstname or lastname are always wrapped in CDATA tags, even if their content doesn't match the typical pattern used by CDATA_WRAPPING_PATTERN.

Motivation:

• Consistent Output: In many integration scenarios (e.g., with legacy systems, XML consumers, or strict XSD schemas), consumers expect certain fields to always use CDATA sections—even when their content doesn't require escaping. This option allows for deterministic XML output by name.

• Better Control: It separates concerns: one can now configure CDATA-wrapping for content-based needs and field-based policies independently.

• Backward Compatible: The feature is fully optional and does not interfere with existing behavior unless the option is explicitly set.