sw::Resource is only used by the Renderer class and the
functionality used is simply one of a WaitGroup. The sync
variables has been changed from a Resource to a WaitGroup
and the Resource class has been removed.

Bug b/133127573

Change-Id: Ic6843be44fcf57f7ac7bef6f3a14726f94761863
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/31689
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>