Unreliable eunit test - `leveled_sst:indexed_list_mixedkeys_bitflip_test/0`

[martinsumner]

Following test failure is possible:

leveled_sst: indexed_list_mixedkeys_bitflip_test...
Preparing key lists for test
*failed*
in function leveled_sst:indexed_list_mixedkeys_bitflip_test/0 (/home/runner/work/leveled/leveled/src/leveled_sst.erl, line 4278)
in call from eunit_test:'-mf_wrapper/2-fun-0-'/2 (eunit_test.erl, line 273)
in call from eunit_test:run_testfun/1 (eunit_test.erl, line 71)
in call from eunit_proc:run_test/1 (eunit_proc.erl, line 531)
in call from eunit_proc:with_timeout/3 (eunit_proc.erl, line 356)
in call from eunit_proc:handle_test/2 (eunit_proc.erl, line 514)
in call from eunit_proc:tests_inorder/3 (eunit_proc.erl, line 456)
in call from eunit_proc:with_timeout/3 (eunit_proc.erl, line 346)
**error:{badmatch,"<E"}
  output:<<"">>

The test assumes that only one position will be returned from find_pos. This is almost always true, but if another key hashes to the same value, then the list may be longer.