This implements a very basic runtime type information used by debug-exposed values.

Bug: b/145351270
Change-Id: I6bd9fe292bd7058307789300d562f7699e12f02b
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/38892Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>