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Fix stack allocation after on-trace stack check.

(cherry picked from commit 204cee2c9)

It is possible that a snapshot topslot is less than the possible topslot
of the Lua stack. In that case, if the Lua stack overflows in
`lj_vmevent_prepare()`, the error is raised inside
`lj_vm_exit_handler()`, which has no corresponding DWARF eh_frame [1],
so it leads to the crash.

This patch fix-ups the topslot of the snapshot on trace exit to the
maximum possible one.

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

[1]: https://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html

Part of tarantool/tarantool#10199

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