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/FileCacheManager.h

@@ -97,7 +97,6 @@ namespace Audio
         TATLPreloadRequestLookup& m_preloadRequests;
         TAudioFileEntries m_audioFileEntries;
 
-        // AZStd::unique_ptr<???> m_memoryHeap; // ToDo: Update to use non-legacy memory: LYN-3792
         size_t m_currentByteTotal;
         size_t m_maxByteTotal;
     };