sd/pptx export: move animation export code to a single file.

Move animation export functions in PowerPointExport to
a single file for further refactor work.

Change-Id: I957599bb293fcdda3d51db48334ef5825b1cba64
Reviewed-on: https://gerrit.libreoffice.org/59731
Tested-by: Jenkins
Reviewed-by: Mark Hung <marklh9@gmail.com>

sd/Library_sdfilt.mk

@@ -63,6 +63,7 @@ $(eval $(call gb_Library_add_exception_objects,sdfilt,\
     sd/source/filter/eppt/pptexsoundcollection \
     sd/source/filter/eppt/pptx-epptbase \
     sd/source/filter/eppt/pptx-epptooxml \
+    sd/source/filter/eppt/pptx-animations \
     sd/source/filter/eppt/pptx-grouptable \
     sd/source/filter/eppt/pptx-stylesheet \
     sd/source/filter/eppt/pptx-text \