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.

tests/unit/application/Parser/ScriptingDefinition/CodeSubstituter.spec.ts

@@ -67,7 +67,7 @@ describe('CodeSubstituter', () => {
         sut.substitute('non empty code', info);
         // assert
         expect(compilerStub.callHistory).to.have.lengthOf(1);
-        const { parameters } = compilerStub.callHistory[0];
+        const parameters = compilerStub.callHistory[0].args[1];
         expect(parameters.hasArgument(testCase.parameter));
         const { argumentValue } = parameters.getArgument(testCase.parameter);
         expect(argumentValue).to.equal(testCase.argument);
@@ -85,7 +85,7 @@ describe('CodeSubstituter', () => {
     sut.substitute(expected, new ProjectInformationStub());
     // assert
     expect(compilerStub.callHistory).to.have.lengthOf(1);
-    expect(compilerStub.callHistory[0].code).to.equal(expected);
+    expect(compilerStub.callHistory[0].args[0]).to.equal(expected);
   });
 });