Misc tidying up around KclValue, etc. (#5653)

* Make some things a little less public

Signed-off-by: Nick Cameron <nrc@ncameron.org>

* Rename KclValue::Array to MixedArray

Signed-off-by: Nick Cameron <nrc@ncameron.org>

* Add settings to KclValue::Function

Signed-off-by: Nick Cameron <nrc@ncameron.org>

* Remove a bunch of dead code, simplifying mock exec and meaning KclValue no longer needs to deserialize

Signed-off-by: Nick Cameron <nrc@ncameron.org>

---------

Signed-off-by: Nick Cameron <nrc@ncameron.org>

src/lib/testHelpers.ts

@@ -81,8 +81,7 @@ class MockEngineCommandManager {
 export async function enginelessExecutor(
   ast: Node<Program>,
   usePrevMemory?: boolean,
-  path?: string,
-  variables?: VariableMap
+  path?: string
 ): Promise<ExecState> {
-  return await executeMock(ast, usePrevMemory, path, variables)
+  return await executeMock(ast, usePrevMemory, path)
 }