fix: move proxy-port properties to proxy plugin and fix CI failures

- Move proxy-port and proxy-ssl-port properties from ports plugin to
  proxy plugin where they conceptually belong
- Generalize proxy:set to handle any property (matching ps:set pattern)
  instead of only handling the type property
- Fix apps:set --global flag parsing (pflag treats --global as a flag,
  not an argument — must be defined explicitly like ps:set does)
- Add missing property-functions source to scheduler-docker-local
  shell scripts (scheduler-enter, scheduler-run, scheduler-deploy,
  check-deploy, bin/scheduler-deploy-process-container)
- Update nginx-vhosts property references from ports to proxy plugin
- Update tests to use proxy:set for proxy-port properties

tests/unit/apps_2.bats

@@ -116,7 +116,7 @@ teardown() {
   echo "output: $output"
   echo "status: $status"
   assert_success
-  run /bin/bash -c "$PLUGIN_CORE_AVAILABLE_PATH/common/prop set ports $TEST_APP proxy-ssl-port 443"
+  run /bin/bash -c "dokku proxy:set $TEST_APP proxy-ssl-port 443"
   echo "output: $output"
   echo "status: $status"
   assert_success

tests/unit/nginx-vhosts_5.bats

@@ -62,7 +62,7 @@ teardown() {
 
 @test "(nginx-vhosts) proxy:build-config (global proxy-port)" {
   local GLOBAL_PORT=30999
-  run /bin/bash -c "$PLUGIN_CORE_AVAILABLE_PATH/common/prop set ports --global proxy-port ${GLOBAL_PORT}"
+  run /bin/bash -c "dokku proxy:set --global proxy-port ${GLOBAL_PORT}"
   echo "output: $output"
   echo "status: $status"
   assert_success
@@ -74,7 +74,7 @@ teardown() {
   check_urls "http://${TEST_APP}.${DOKKU_DOMAIN}:${GLOBAL_PORT}"
   assert_http_success "http://${TEST_APP}.${DOKKU_DOMAIN}:${GLOBAL_PORT}"
 
-  run /bin/bash -c "$PLUGIN_CORE_AVAILABLE_PATH/common/prop del ports --global proxy-port"
+  run /bin/bash -c "dokku proxy:set --global proxy-port"
   echo "output: $output"
   echo "status: $status"
   assert_success