Allocators for audio system file cache (#1485)

* Reinstates an allocator for FileCacheManager

Replaces the allocator that was removed during redcode that is used for
loading banks.  Default schema for now to get things working again.

* Update path functions to AZ::IO::Path

Removes old PathUtil functions in favor of AZ::IO::Path apis.

* Update the audio allocator classes

Cleans up the audio allocator classes a bit.

* Addresses PR feedback

Updates some code to handle nullptr a bit better, and improve log
messages.

* Updates to audio CVars and address feedback

Per feedback, converted more of the audio cvars to AZ_CVAR, but not all
of them could be converted at this time.  Moved audio allocator
initialization to system component ctor/dtor to give RAII.  Updated
location of a PAL file.

* Updates the copyright of the file added in this PR

Merged copyright changes, so need to update new files.

Gems/AudioSystem/Code/Source/Engine/ATL.cpp

@@ -505,7 +505,7 @@ namespace Audio
                 case eAMRT_LOSE_FOCUS:
                 {
                 #if !defined(AUDIO_RELEASE)
-                    if (g_audioCVars.m_nIgnoreWindowFocus == 0 && (m_nFlags & eAIS_IS_MUTED) == 0)
+                    if (!Audio::CVars::s_IgnoreWindowFocus && (m_nFlags & eAIS_IS_MUTED) == 0)
                 #endif // !AUDIO_RELEASE
                     {
                         auto it = m_cTriggers.find(ATLInternalControlIDs::LoseFocusTriggerID);
@@ -525,7 +525,7 @@ namespace Audio
                 case eAMRT_GET_FOCUS:
                 {
                 #if !defined(AUDIO_RELEASE)
-                    if (g_audioCVars.m_nIgnoreWindowFocus == 0 && (m_nFlags & eAIS_IS_MUTED) == 0)
+                    if (!Audio::CVars::s_IgnoreWindowFocus && (m_nFlags & eAIS_IS_MUTED) == 0)
                 #endif // !AUDIO_RELEASE
                     {
                         AudioSystemImplementationNotificationBus::Broadcast(&AudioSystemImplementationNotificationBus::Events::OnAudioSystemGetFocus);