Fix compiler bug with nested optional arguments

This commit fixes compiler bug where it fails when optional values are
compiled into absent values in nested calls.

- Throw exception with more context for easier future debugging.
- Add better validation of argument values for nested calls.
- Refactor `FunctionCallCompiler` for better clarity and modularize it
  to make it more maintainable and testable.
- Refactor related interface to not have `I` prefix, and
  function/variable names for better clarity.

Context:

Discovered this issue while attempting to call
`RunInlineCodeAsTrustedInstaller` which in turn invokes `RunPowerShell`
for issue #246. This led to the realization that despite parameters
flagged as optional, the nested argument compilation didn't support
them.

src/application/Parser/Script/Compiler/Function/SharedFunction.ts

@@ -1,4 +1,4 @@
-import { IFunctionCall } from './Call/IFunctionCall';
+import { FunctionCall } from './Call/FunctionCall';
 
 import {
   FunctionBodyType, IFunctionCode, ISharedFunction, ISharedFunctionBody,
@@ -8,7 +8,7 @@ import { IReadOnlyFunctionParameterCollection } from './Parameter/IFunctionParam
 export function createCallerFunction(
   name: string,
   parameters: IReadOnlyFunctionParameterCollection,
-  callSequence: readonly IFunctionCall[],
+  callSequence: readonly FunctionCall[],
 ): ISharedFunction {
   if (!callSequence || !callSequence.length) {
     throw new Error(`missing call sequence in function "${name}"`);
@@ -38,7 +38,7 @@ class SharedFunction implements ISharedFunction {
   constructor(
     public readonly name: string,
     public readonly parameters: IReadOnlyFunctionParameterCollection,
-    content: IFunctionCode | readonly IFunctionCall[],
+    content: IFunctionCode | readonly FunctionCall[],
     bodyType: FunctionBodyType,
   ) {
     if (!name) { throw new Error('missing function name'); }
@@ -46,7 +46,7 @@ class SharedFunction implements ISharedFunction {
     this.body = {
       type: bodyType,
       code: bodyType === FunctionBodyType.Code ? content as IFunctionCode : undefined,
-      calls: bodyType === FunctionBodyType.Calls ? content as readonly IFunctionCall[] : undefined,
+      calls: bodyType === FunctionBodyType.Calls ? content as readonly FunctionCall[] : undefined,
     };
   }
 }