cli, entry, lang: Add an entry package for embeddable CLI's

This adds a new entry package that allows embedded programs to exist
inside of mgmt. This took a lot of refactoring to get the API right, but
I think it's incredibly elegant now. There is a chance we tweak things a
bit, but it's a good first start. All-in-one programs are coming soon!

lang/core/embedded/embedded.go

@@ -0,0 +1,23 @@
+// Mgmt
+// Copyright (C) 2013-2024+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package coreembedded
+
+const (
+	// ModuleName is the prefix given to all the functions in this module.
+	ModuleName = "embedded"
+)