Add lexical scope and redefining variables in functions (#3015)

* Fix to allow variable shadowing inside functions

* Implement closures

* Fix KCL test code to not reference future tag definition

* Remove tag declarator from function parameters

This is an example where the scoping change revealed a subtle issue
with TagDeclarators.  You cannot bind a new tag using a function
parameter.

The issue is that evaluating a TagDeclarator like $foo binds an
identifier to its corresponding TagIdentifier, but returns the
TagDeclarator.  If you have a TagDeclarator passed in as a parameter
to a function, you can never get its corresponding TagIdentifier.

This seems like a case where TagDeclarator evaluation needs to be
revisited, especially now that we have scoped tags.

* Fix to query return, functions, and tag declarator AST nodes correctly

src/lang/artifact.test.ts

@@ -16,7 +16,7 @@ const mySketch001 = startSketchOn('XY')
   // |> rx(45, %)`
     const programMemory = await enginelessExecutor(parse(code))
     // @ts-ignore
-    const sketch001 = programMemory?.root?.mySketch001
+    const sketch001 = programMemory?.get('mySketch001')
     expect(sketch001).toEqual({
       type: 'SketchGroup',
       on: expect.any(Object),
@@ -66,7 +66,7 @@ const mySketch001 = startSketchOn('XY')
   |> extrude(2, %)`
     const programMemory = await enginelessExecutor(parse(code))
     // @ts-ignore
-    const sketch001 = programMemory?.root?.mySketch001
+    const sketch001 = programMemory?.get('mySketch001')
     expect(sketch001).toEqual({
       type: 'ExtrudeGroup',
       id: expect.any(String),
@@ -146,7 +146,7 @@ const sk2 = startSketchOn('XY')
 `
     const programMemory = await enginelessExecutor(parse(code))
     // @ts-ignore
-    const geos = [programMemory?.root?.theExtrude, programMemory?.root?.sk2]
+    const geos = [programMemory?.get('theExtrude'), programMemory?.get('sk2')]
     expect(geos).toEqual([
       {
         type: 'ExtrudeGroup',