Title: uhv: oghttp2: disable header validations based on compile flag

Description:
oghttp2 is being adopted in Envoy and has recently add a method of disabling header validations through a configuration setting. Using a compile time ifdef, disable H2 header validation within the parsing library when building UHV. This will be very similar to H1. We plan on using the new validate_http_headers exposed by the external_quiche_http2::adapter::OgHttp2Adapter::Options class, most likely within the Http2Options constructor.

Refs #19751