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Emit sunk IR_NEWREF only once per key on snapshot replay.

Thanks to Sergey Kaplun and Peter Cawley.

(cherry-picked from commit 1761fd2ef)

Assume we have the parent trace with the following IRs:

| 0001 }  tab TNEW   #0    #0
| 0002 }  p32 NEWREF 0001  "key"
| 0003 }  fal HSTORE 0002  false
| ....        SNAP   #1   [ ---- ---- 0001 ---- ]
| 0004 >  num SLOAD  #1    T
| ....        SNAP   #2   [ ---- ---- 0001 ]
| 0005 >  num EQ     0004  0004
| 0006 }  tru HSTORE 0002  true
| ....        SNAP   #3   [ ---- ---- 0001 true ]

The side trace for the third snapshot emits the following IRs:

| 0001    tab TNEW   #0    #0
| 0002    p32 NEWREF 0001  "key"
| 0003    fal HSTORE 0002  false
| 0004    p32 NEWREF 0001  "key"
| 0005    tru HSTORE 0004  true

As we can see, `NEWREF` is emitted twice. This is a violation of its
semantics, so the second store isn't noticeable.

This patch prevents the second emitting of IR NEWREF by checking the last
one emitted NEWREF IR. There is no need to check NEWREFs beyond since
it guarantees the snapshot is taken after it, because it may cause table
rehashing, so all prior results are invalidated.

Sergey Kaplun:
* added the description and the test for the problem

Resolves tarantool/tarantool#7937
Part of tarantool/tarantool#9145

Reviewed-by: Maxim Kokryashkin <m.kokryashkin@tarantool.org>
Reviewed-by: Sergey Bronnikov <sergeyb@tarantool.org>
Signed-off-by: Igor Munkin <imun@tarantool.org>

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