extract CppunitTest_sw_ooxmlfieldexport from CppunitTest_sw_ooxmlimport

before:
$ time make -sr CppunitTest_sw_ooxmlexport
real    4m5.728s

after:
$ time make -sr CppunitTest_sw_ooxmlexport
real    3m24.446s

and the new CppunitTest_sw_ooxmlfieldexport can run in parallel.

Change-Id: I5a1d121f51e2d09a1c2126a33484e956c5c706a8

sw/Module_sw.mk

@@ -55,6 +55,7 @@ $(eval $(call gb_Module_add_slowcheck_targets,sw,\
     CppunitTest_sw_htmlexport \
     CppunitTest_sw_macros_test \
     CppunitTest_sw_ooxmlexport \
+    CppunitTest_sw_ooxmlfieldexport \
     CppunitTest_sw_ooxmlsdrexport \
     CppunitTest_sw_ooxmlw14export \
     CppunitTest_sw_ooxmlimport \