Remove ProgramLinkedResources from ProgramExecutable. Instead of storing the entire LinkedResources struct, we can keep it only for the duration of the linking calls. Refactoring change only. It sets the stage for more refactoring. This change also switches the link call to use LinkingState's ProgramLinkedResources directly to avoid the need to copy the varying packing or use a pointer. Bug: angleproject:4514 Bug: angleproject:5496 Change-Id: Iefea3c16a33213dc338cc54efaa7c3064ea6ae08 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2601403 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>