In SERVER-43187, the action_type.h header went from being generated to being non-generated.

Because the filename did not include the _gen.h suffix on the old branches, the renaming has created a situation where moving back and forth from v4.4 (and presumably older) to master causes a build break.

We should probably either rename the action_type.h header on master, or adjust it on old stables so that the generator produces action_type_gen.h along with a forwarding header.

This would remove the build breakage that happens while moving across these branches.