vktrace: Convert tracing library to an actual vulkan layer library

Caveats:
 Disable codegen for time being for this layer.
 Only one instance and device dispatch table supported in this layer.
 Must use env vars to enable the layer in vktrace -p
 Extensions are always enabled currently

Conflicts:
	vktrace/src/vktrace_layer/vktrace_lib_trace.c
2 files changed