Moved the SettingsRegistryFileReader class to more general IO Reader (#4189)

The new FileReader class allows using either a FileIOBase or SystemFile
classes for reading files.
If a non-nullptr FileIOBase is supplied, the FileIOBase is used,
otherwise SystemFile is used.

Updated the SettingsRegistryMergeUtils
`MergeSettingsToRegistry_ConfigFile` function to use the FileReader.

This allows .cfg such as the autoexec.cfg to be read using FileIO,
therefore allowing it to be read from the engine.pak file.

Because the AZ::Console::ExecuteConfigFile uses the
`MergeSettingsToRegistry_ConfigFile` function for merging *.cfg files to
the SettingsRegistry, this allows the AZ::Console to run console
commands from files within pak files thanks to the ArchiveFileIO being
the default FileIOBase instance

Signed-off-by: lumberyard-employee-dm <56135373+lumberyard-employee-dm@users.noreply.github.com>

Code/Framework/AzCore/Tests/IO/FileReaderTests.cpp

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+#include <AzCore/IO/FileReader.h>
+#include <FileIOBaseTestTypes.h>
+#include <AzCore/UnitTest/TestTypes.h>
+
+namespace UnitTest
+{
+    template <typename FileIOType>
+    class FileReaderTestFixture
+        : public ScopedAllocatorSetupFixture
+    {
+    public:
+        void SetUp() override
+        {
+            if constexpr (AZStd::is_same_v<FileIOType, TestFileIOBase>)
+            {
+                m_fileIo = AZStd::make_unique<TestFileIOBase>();
+            }
+        }
+
+        void TearDown() override
+        {
+            m_fileIo.reset();
+        }
+
+    protected:
+        AZStd::unique_ptr<AZ::IO::FileIOBase> m_fileIo{};
+    };
+
+    using FileIOTypes = ::testing::Types<void, TestFileIOBase>;
+
+    TYPED_TEST_CASE(FileReaderTestFixture, FileIOTypes);
+
+    TYPED_TEST(FileReaderTestFixture, ConstructorWithFilePath_OpensFileSuccessfully)
+    {
+        AZ::IO::FileReader fileReader(this->m_fileIo.get(), AZ::IO::SystemFile::GetNullFilename());
+        EXPECT_TRUE(fileReader.IsOpen());
+    }
+
+    TYPED_TEST(FileReaderTestFixture, Open_OpensFileSucessfully)
+    {
+        AZ::IO::FileReader fileReader;
+        fileReader.Open(this->m_fileIo.get(), AZ::IO::SystemFile::GetNullFilename());
+        EXPECT_TRUE(fileReader.IsOpen());
+    }
+
+    TYPED_TEST(FileReaderTestFixture, Eof_OnNULDeviceFile_Succeeds)
+    {
+        AZ::IO::FileReader fileReader(this->m_fileIo.get(), AZ::IO::SystemFile::GetNullFilename());
+        EXPECT_TRUE(fileReader.Eof());
+    }
+
+    TYPED_TEST(FileReaderTestFixture, GetFilePath_ReturnsNULDeviceFilename_Succeeds)
+    {
+        AZ::IO::FileReader fileReader(this->m_fileIo.get(), AZ::IO::SystemFile::GetNullFilename());
+        AZ::IO::FixedMaxPath filePath;
+        EXPECT_TRUE(fileReader.GetFilePath(filePath));
+        AZ::IO::FixedMaxPath nulFilename{ AZ::IO::SystemFile::GetNullFilename() };
+        if (this->m_fileIo)
+        {
+            EXPECT_TRUE(this->m_fileIo->ResolvePath(nulFilename, nulFilename));
+        }
+        EXPECT_EQ(nulFilename, filePath);
+    }
+
+}   // namespace UnitTest

Code/Framework/AzCore/Tests/azcoretests_files.cmake

@@ -37,6 +37,7 @@ set(FILES
     FileIOBaseTestTypes.h
     Geometry2DUtils.cpp
     Interface.cpp
+    IO/FileReaderTests.cpp
     IO/Path/PathTests.cpp
     IPC.cpp
     Jobs.cpp