As d5c89cc proved not to be NFC, prior to this change, duplicate
`MemoryAccess` entries were being added to the worklist in
`isWriteAtEndOfFunction`, prematurely reaching the exploration
limit. When `MemorySSAScanLimit` cutoff is set to 4, the store
was previously not eliminated. Introduce a regression test for
additional validation. The test is a simplified variant of function
`ntlmssp_create_session_key`, coming from @dtcxzyw/llvm-opt-benchmark,
bench/wireshark/original/packet-ntlmssp.c.ll.
10d720b5b4