125044: - use field's content cache on <SwTxtFld> construction only

... for clipboard documents

- assure invalidation and updates on code to update fields

(cherry picked from commit 3d4d98d4d98bc62474ec295cdc4d070a01dcac13)

The substantial bug was already fixed years ago by commit
9519deda120b73b72e75d89c3b2ae3d66220ec2d

Conflicts:
	sw/inc/txtannotationfld.hxx
	sw/inc/txtfld.hxx
	sw/source/core/crsr/crstrvl.cxx
	sw/source/core/txtnode/atrfld.cxx
	sw/source/core/txtnode/thints.cxx

Change-Id: Ib4965c5d443b60bab11bad1a9249fc6547976a3c