Include bitmap images in PDF plots, preview, and printing

Include decoded IMAGE/OLE content in the shared PDF plotting path,
with clipping, transforms, transparency, draw order, and resource reuse.
Use named page content for export and printing.

Fixes #1266

tests/fixtures/embedded-image-print.md

@@ -0,0 +1,8 @@
+Synthetic regression fixture for #1266. Generated with ezdxf/Pillow from basic
+geometry; it contains no external references or customer drawing content.
+
+Layout1 has an INSERT of SyntheticImage at (2, 4). That block contains one
+OLE2FRAME whose compound-file CONTENTS stream embeds a 64 x 32 BMP: red on
+the left, blue on the right, with a green diagonal from top-left to bottom-right.
+The frame occupies (0, 0) to (2, 1) in the block. Text and a triangle provide
+vector controls for manually opening the fixture and checking Plot Preview.