So that the print value's 'fmt' is a dynamic function instead of a constexpr.

Let's us do smarter stuff based on the type and value, and will allow us to move functionality from overloads on rr::PrintValue to PrintValue::Ty template specializations.

Also fix a bunch of missing integer expansion casts which were missing from ca8e3d7c.

Bug: b/140287657
Change-Id: I7e18c35ae23d8a2dd6b726562ae1348a1b7075dd
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/32049Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>