Breakpoints on nodes in deleted functions are not cleared

Might be a simpler repro than this, but take a look at revision 1 of PreRolledBoxes in FortniteMain to see an asset affected by this. It was duplicated from StoreRoot which had breakpoints in some of the nodes in its functions. Most functions in PreRolledBoxes were deleted after the duplicate, but the breakpoints on the nodes in those functions were not removed, causing the function graphs to remain in the package and emit warnings when the asset was loaded.

Possible easy repro (untested):

1) Make a blueprint

2) Make a function in the blueprint

3) Add a node to that function, put a breakpoint on it, compile save

4) Run `obj list2 class=breakpoint`

4) Delete the function, save the blueprint

5) Reload the blueprint

6) run `obj list2 class=breakpoint` - note that it has the same number of breakpoints as after step 3)