List all files, including those that have no coverage.
Emit spans that were compiled, but not covered.
Emit a % coverage per file.

Bug: b/152192800
Fixes: b/153182184
Change-Id: I31c831273a8d3ee89c7ce0737b6e05398ff4f51b
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/43491
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>