Replace hardcoded inheritFont() with InheritFont InsetLayout tag

Replace hardcoded inheritFont() with InheritFont InsetLayout tag

Each removed inheritFont method is replaced by a 'InheritFont false'
line in the relevant InsetLayout entry.

Add code to layout2layout that does this automatically when the entry
is missing.

The case of InsetScript is special, since the inheritFont() was not
needed here: the default is indeed true.

Fixes bug #12238.