layers: Clean up PIPELINE_NODE using safe_struct

PIPELINE_NODE was storing ptrs from the app and has some ugly initialization code
for the gfx pipeline create struct. This commit switches pipeline node to use
safe_struct wrappers for Gfx and Compute create info.
There were also some bugs found in the safe_struct wrappers making this migration
so those are cleaned up in this commit as well.
5 files changed