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/shared/Stubs/CodeSegmentMergerStub.ts

@@ -0,0 +1,16 @@
+import { CodeSegmentMerger } from '@/application/Parser/Script/Compiler/Function/Call/Compiler/CodeSegmentJoin/CodeSegmentMerger';
+import { CompiledCode } from '@/application/Parser/Script/Compiler/Function/Call/Compiler/CompiledCode';
+import { CompiledCodeStub } from './CompiledCodeStub';
+import { StubWithObservableMethodCalls } from './StubWithObservableMethodCalls';
+
+export class CodeSegmentMergerStub
+  extends StubWithObservableMethodCalls<CodeSegmentMerger>
+  implements CodeSegmentMerger {
+  public mergeCodeParts(codeSegments: readonly CompiledCode[]): CompiledCode {
+    this.registerMethodCall({
+      methodName: 'mergeCodeParts',
+      args: [codeSegments],
+    });
+    return new CompiledCodeStub();
+  }
+}