refactor: switch detected builder so first one wins

Also rename internal cnb references to pack (where possible).

plugins/builder-dockerfile/builder-detect

@@ -8,6 +8,24 @@ trigger-builder-dockerfile-builder-detect() {
   declare trigger="builder-detect"
   declare APP="$1" SOURCECODE_WORK_DIR="$2"
 
+  # hack: unfortunately our legacy code requires that buildpacks
+  #       are detected before dockerfile support is detected
+  #       as such, we need to force-check the herokuish and pack
+  #       builders before allowing the dockerfile check to succeed
+  #       in a future release, we may drop this hack, but for now,
+  #       such is life
+  if [[ -f "$PLUGIN_ENABLED_PATH/builder-herokuish/builder-detect" ]]; then
+    if [[ -n "$($PLUGIN_ENABLED_PATH/builder-herokuish/builder-detect "$APP" "$SOURCECODE_WORK_DIR")" ]]; then
+      return
+    fi
+  fi
+
+  if [[ -f "$PLUGIN_ENABLED_PATH/builder-pack/builder-detect" ]]; then
+    if [[ -n "$($PLUGIN_ENABLED_PATH/builder-pack/builder-detect "$APP" "$SOURCECODE_WORK_DIR")" ]]; then
+      return
+    fi
+  fi
+
   if [[ -f "$SOURCECODE_WORK_DIR/Dockerfile" ]]; then
     echo "dockerfile"
     return