Add GlobalProtect SAML based authentication support with OpenConnect VPN

Pass HTTP response headers to libopenconnect SAML handling functionality.
libopenconnect will process the headers and authenticate with GlobalProtect
gateways.

This change depends on Qt>=6.6 for the needed changes in QtWebEngine that
enable HTTP response header extraction.

BUG: 444500


Signed-off-by: Rahul Rameshbabu <sergeantsagara@protonmail.com>