A CXFA_Node can only be in one packet

When a CXFA_Node is created it's created as part of a specific packet.
Previously the code would accept an XFA_XDPPACKET which was stored
internally. This had the potential to allow a node to exist in multiple
packets.

This CL changes the XFA_XDPPacket to the XFA_PacketType enum class and
cleans up a lot of uses to use the more specific packet type.

Change-Id: I7fc8c843bfa6bd32295ae58a26bcec311e43c4b0
Reviewed-on: https://pdfium-review.googlesource.com/20012
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

xfa/fxfa/parser/cxfa_documentassembly.cpp

diff --git a/xfa/fxfa/parser/cxfa_documentassembly.cpp b/xfa/fxfa/parser/cxfa_documentassembly.cpp
index 5ddc90f..146071d 100644
--- a/xfa/fxfa/parser/cxfa_documentassembly.cpp
+++ b/xfa/fxfa/parser/cxfa_documentassembly.cpp
@@ -18,7 +18,7 @@
 }  // namespace
 
 CXFA_DocumentAssembly::CXFA_DocumentAssembly(CXFA_Document* doc,
-                                             XFA_XDPPACKET packet)
+                                             XFA_PacketType packet)
     : CXFA_Node(doc,
                 packet,
                 XFA_XDPPACKET_Config,