Forwarded headers are now processed before ServerWebExchange is created
through ForwardedHeaderTransformer which has the same logic as the
ForwardedHeaderFilter but works on the request only.

ForwardedHeaderFilter is deprecated as of 5.1 but if registered it is
removed from the list of filters and ForwardedHeaderTransformer is used
instead.

Issue: SPR-17072

Issue: SPR-16972

Issue: SPR-16298

Issue: SPR-15718

Replace the more limited List-based methods to add filtes and exception
handlers with Consumer<List<?>> variants.

Issue: SPR-15074