refactor: move misplaced TF_LITE_REMOVE_VIRTUAL_DELETEs to private:

[rkuester]

Move several TF_LITE_REMOVE_VIRTUAL_DELETE declarations that are
wrongly in a public section of their classes. To have the intended
effect, as documented in t/l/m/compatibility.h, these must be in a
private section.

BUG=see description

[suleshahid]

Seems like these were moved out of private intentionally? e814105

[rkuester]

If the right fix for whatever that problem was is to make the destructors public: accessible, it certainly breaks the intent, naming, and comments relating to the define TF_LITE_REMOVE_VIRTUAL_DELETE. It might be a sign those classes are called in unintended ways. If the destructors are indeed desired, they should probably be defined without the macro.

This commit is actually from quite a while ago, and I've forgotten now whether I had a need to fix it, or whether I just spotted the inconsistency and cleaned up. I'll drop this PR for now, and resurrect it if this becomes necessary for the compression feature #2636.