LibAudio+LibRIFF: Move general RIFF handling to LibRIFF

This splits the RIFFTypes header/TU into the WAV specific parts, which
move to WavTypes.h, as well as the general RIFF parts which move to the
new LibRIFF.

Sidenote for the spec comments: even though they are linked from a site
that explains the WAV format, the document is the (an) overall RIFF spec
from Microsoft. A better source may be used later; the changes to the
header are as minimal as possible.

Meta/Lagom/CMakeLists.txt

@@ -436,6 +436,7 @@ if (BUILD_LAGOM)
         PDF
         Protocol
         Regex
+        RIFF
         SoftGPU
         SQL
         Syntax

Meta/gn/secondary/Userland/Libraries/LibAudio/BUILD.gn

@@ -13,7 +13,6 @@ shared_library("LibAudio") {
     "PlaybackStream.cpp",
     "QOALoader.cpp",
     "QOATypes.cpp",
-    "RIFFTypes.cpp",
     "SampleFormats.cpp",
     "UserSampleQueue.cpp",
     "VorbisComment.cpp",