In rebalance/split operations, temporary cursors need to be visible
to propagate fixups

Ignore sub-cursors that shouldn't be fixed up

Set a valid txn so that cursor fixup code works on the shadows

It was reporting spurious errors due to uninit'd cursors

Adjustments can't be skipped, in recursive calls each level must
fixup their own level.

When deleting a dupsort key, if other cursors pointed at that key,
set them to uninit'd, not EOF. They no longer have anything to
point at.

Just tell explicitly which direction we moved/merged from

Deleting the merged page requires bumping down other ki's
of the page's parent.

Keep dirty_room sync'd with dirty_list

dummy flags must be init'd due to 3d46d550

Check for top of stack. Usually the cursor only has height 1 when
calling page_split, but not always.

When collapsing root, must adjust entire cursor stack

Was using the pre-touch dst page pointer instead of the touched page

When moving a node from one page to another, make sure other cursors'
parent index gets adjusted too.

When moving a node from the right neighbor, a different
adjustment is needed.

Don't adjust other cursors when we added a node on the right.

ITS#8258, ITS#7829 fixes checked parent index to see if we were moving
from a left neighbor. Should have just checked to see if current index
was 0, meaning we added on the left. (Parent index may not tell us
anything meaningful after a nested rebalance.)

Parent mc_ki wasn't adjusted if new_indx was > split point

The parent's mc_ki has changed. We need to fix that up as well
in other cursors.

No effect on current code.