txm: rollback all statements related to space on alter

There was a bug that led to dirty read after space alter. For the
simplicity sake imagine following setup:

-- space 's' is empty
tx1:begin()
tx1('s:replace{2}')
s:alter({format = format})
s:select{}

Last select returns tuple {2}, however transaction tx1 hasn't been
committed. This happens due to the fact that during alter operation we
create new space, swap all unchanged parts of old space and then delete
old space. During removal of old space we also clean-up all stories
related to it. In turn story destruction may make dirty tuple clean in
case it remains in the index. In the previous implementation there was
no removal of uncommitted tuples from corresponding indexes. So let's
rollback all changes happened to the space right in time of alter. It is
legal since DDL operation anyway aborts ALL other transactions.

Closes #6318
Closes #6263