Add ability to save .rdc file thumbnail in formats other than JPEG

By default RenderDoc saves captured frame thumbnail image as JPEG which
is lossy compression and makes it difficult to use as a reference image
for testing. Added an option to save thumbnails in different formats.

In order not to change the binary serialization format of .rdc files, if
the thumbnail format is not JPEG, a default JPEG thumbnail is still
saved in the file header as before, while the actual thumbnail is saved
as an additional chunk in the binary sections list. Older versions of
RenderDoc will just ignore this section and still use the legacy JPEG
thumbnail.

Change-Id: Icbf4fbd629719b49868fb785a656f6c7c9946ef9

renderdoc/api/replay/renderdoc_tostr.inl

@@ -852,6 +852,7 @@ std::string DoStringise(const SectionType &el)
     STRINGISE_ENUM_CLASS_NAMED(Notes, "renderdoc/ui/notes");
     STRINGISE_ENUM_CLASS_NAMED(ResourceRenames, "renderdoc/ui/resrenames");
     STRINGISE_ENUM_CLASS_NAMED(AMDRGPProfile, "amd/rgp/profile");
+    STRINGISE_ENUM_CLASS_NAMED(ExtendedThumbnail, "renderdoc/internal/exthumb");
   }
   END_ENUM_STRINGISE();
 }

renderdoc/api/replay/replay_enums.h

@@ -76,6 +76,13 @@ version of RenderDoc that addes a new section type. They should be considered eq
   This section contains a .rgp profile from AMD's RGP tool, which can be extracted and loaded.
 
   The name for this section will be "amd/rgp/profile".
+
+.. data:: ExtendedThumbnail
+
+  This section contains a thumbnail in format other than JPEG. For example, when it needs to be
+  lossless.
+
+  The name for this section will be "renderdoc/internal/exthumb".
 )");
 enum class SectionType : uint32_t
 {
@@ -87,6 +94,7 @@ enum class SectionType : uint32_t
   Notes,
   ResourceRenames,
   AMDRGPProfile,
+  ExtendedThumbnail,
   Count,
 };