Basic RenderPass implementation

Basic RenderPass implementation

RenderPass information is required for RenderPass related commands,
like clearing attachments. This cl adds storage for attachments,
subpasses and dependencies related information in the RenderPass
objects and stores all this information in new class members.

Bug b/119620965

Change-Id: I19d8b8465c807755881de6471700a119082575f8
Reviewed-on: https://swiftshader-review.googlesource.com/c/23788
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>