fix: correct entering running containers

This functionality was broken due to a refactor of argument handling in a previous release.

In addition to the fix, all the functionality was moved to scheduler-enter, which allows scheduler plugins to implement ways of entering containers in the relevant scheduler.

Closes #3972

docs/development/plugin-triggers.md

@@ -1683,6 +1683,25 @@ DOKKU_SCHEDULER="$1"; APP="$2"; FORCE_CLEANUP="$3";
 # TODO
 ```
 
+### `scheduler-enter`
+
+> Warning: The scheduler plugin trigger apis are under development and may change
+> between minor releases until the 1.0 release.
+
+- Description: Allows you to enter a running container for a given app
+- Invoked by: `dokku enter`
+- Arguments: `$DOKKU_SCHEDULER $APP $@`
+- Example:
+
+```shell
+#!/usr/bin/env bash
+
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+DOKKU_SCHEDULER="$1"; APP="$2"; ARGS="$@"
+
+# TODO
+```
+
 ### `scheduler-inspect`
 
 > Warning: The scheduler plugin trigger apis are under development and may change
@@ -1720,6 +1739,7 @@ DOKKU_SCHEDULER="$1"; APP="$2";
 
 # TODO
 ```
+
 ### `scheduler-logs`
 
 > Warning: The scheduler plugin trigger apis are under development and may change