Broken HTTPS connect on forward proxy

Commit cf58a91ccd3048f3f0a540463ad8609ae2ce1209 (TS-5040) broke forward proxy connectivity to HTTPS sites.
Previous behaviour: ATS would create a TLS connection to origin server
Current behaviour: ATS issues a "CONNECT host:port" command (in the clear) to the server, which is rejected by the server.

(Tested against commit 79ef0d5980b168c5d3292e180ba15f458fe5bea9 as one example of "previous")

Both values for proxy.config.http.forward_connect_method (0 and 1) exhibit this behaviour.

Using default configuration, plus forward proxy:

1. https://docs.trafficserver.apache.org/records.config#url-remap-rules
2. https://docs.trafficserver.apache.org/en/latest/admin-guide/files/remap.config.en.html
   ##############################################################################
   -CONFIG proxy.config.url_remap.remap_required INT 1
   +CONFIG proxy.config.url_remap.remap_required INT 0
3. https://docs.trafficserver.apache.org/records.config#proxy-config-url-remap-pristine-host-hdr
   CONFIG proxy.config.url_remap.pristine_host_hdr INT 0
4. https://docs.trafficserver.apache.org/records.config#reverse-proxy
   -CONFIG proxy.config.reverse_proxy.enabled INT 1
   +CONFIG proxy.config.reverse_proxy.enabled INT 0

Behaviour can be viewed by logging network traffic (tcpdump port 443).