LYN-2723: Fixes issues with bad project or engine paths (#369)

* Setup NativeUIRequests as an AZ::Interface.  Adds a NativeUISystemComponent to AzFramework Application.

* Renames NativeUISystemComponent (class) to NativeUISystem, since it's no longer a Component.

* Minor update to SettingsRegistryInterface::Remove doc-comments for accuracy.

* Fixes to make an early fatal shutdown of Editor occur without crash.

* LYN-2723: Updates startup to handle errors: engine root is empty, no valid project.json found (mismatched engine name), or bad project path (launch project picker dialog).

* LYN-2723: Minor formatting/spelling edits.

* LYN-2723: Moves ParseCommandLine from ComponentApplication to SettingsRegistryMergeUtils so it can be used in more places.

* Misc fixes. 'wait_for_connect' setting wasn't being properly applied to AP connection settings. Fix infinite loop in CCmdLine::Next.

* LYN-2723: Addresses review feedback.

* LYN-2723: Reverts some changes that caused a unit test to fail.

* LYN-2723: Reverts one more change that was unnecessary.

Code/Tools/RC/ResourceCompiler/main.cpp

@@ -579,6 +579,8 @@ int rcmain(int argc, char** argv, [[maybe_unused]] char** envp)
             // on the command line
             AZ::CommandLine commandLine;
             commandLine.Parse(argc, argv);
+            AZ::SettingsRegistryMergeUtils::ParseCommandLine(commandLine);
+
             AZ::SettingsRegistryImpl settingsRegistry;
             AZ::SettingsRegistryMergeUtils::MergeSettingsToRegistry_Bootstrap(settingsRegistry);
             AZ::SettingsRegistryMergeUtils::MergeSettingsToRegistry_O3deUserRegistry(settingsRegistry, AZ_TRAIT_OS_PLATFORM_CODENAME, {});