[Windows App SDK Installer] Functional Test Fixes

[ssparach]

This PR fixes the following issues for the Windows App SDK Installer functional tests:

• The test expects the installer to be copied to a different directory instead of where the test module is located.
• The tests do not construct the installer path correctly
  Error: Verify:IsTrue(std::filesystem::exists(GetInstallerPath())) [File: \installer\test\InstallerFunctionalTests\FunctionalTests.cpp, Function: WindowsAppRunTimeInstallerTests::FunctionalTests::ClassInit, Line 32]
  Error: TAEF: Setup fixture ‘WindowsAppRunTimeInstallerTests::FunctionalTests::ClassInit’ for the scope ‘WindowsAppRunTimeInstallerTests::FunctionalTests’ failed.
• The installer does not return the expected exit code when run with the argument --help.
  Error: Verify: AreEqual(S_OK, result) - Values (0, -2147024895), \installer\test\InstallerFunctionalTests\FunctionalTests.cpp, Function: WindowsAppRuntimeInstallerTests::FunctionalTests::VerifyArgsHelp, Line: 68

The changes were confirmed by executing the functional tests and verifying that they all passed successfully.

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