Updated custom request overrides to better match original intent

Updated custom request overrides to better match original intent

This updates the custom Request handler to provide only the scheme and
host on the `getSchemeAndHttpHost` call, instead of providing the whole
APP_URL value, while adding an override to the 'getBaseUrl' to use the
APP_URL content instead of the guessed/detected Symfony value.

Untested apart from simple local setup.

Related to #2765