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/Call/ParsedFunctionCall.ts

@@ -0,0 +1,16 @@
+import { IReadOnlyFunctionCallArgumentCollection } from './Argument/IFunctionCallArgumentCollection';
+import { FunctionCall } from './FunctionCall';
+
+export class ParsedFunctionCall implements FunctionCall {
+  constructor(
+    public readonly functionName: string,
+    public readonly args: IReadOnlyFunctionCallArgumentCollection,
+  ) {
+    if (!functionName) {
+      throw new Error('missing function name in function call');
+    }
+    if (!args) {
+      throw new Error('missing args');
+    }
+  }
+}