Make literal picker independent of theory explanation order

[dewert99]

While working on #11 I noticed that some of the performance changes were caused by differences in the literal picking order which themselves were cause by the explanations having different orders (even though they were always the same set). For this PR I modified batsat's literal picker to ignore the explanation order so that #11 could be better compared.

[codspeed-hq]

CodSpeed Performance Report

Merging #14 will degrade performances by 29.75%

_{Comparing detirministic (6a184d4) with main (c12dce5)}

Summary

⚡ 13 improvements
❌ 6 (👁 6) regressions
✅ 61 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	detirministic	Change
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_brp.5.prop1_ab_core_max.smt2	559.1 ms	469.4 ms	+19.11%
👁	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_brp.6.prop1_ab_min_max.smt2	326.1 ms	464.3 ms	-29.75%
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_brp2.4.prop2_ab_min_max.smt2	423.7 ms	384.3 ms	+10.25%
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_cambridge.6.prop2_ab_min_max.smt2	1.4 s	1.1 s	+18.84%
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_elevator.3.prop1_ab_core_max.smt2	109.6 ms	91.4 ms	+19.89%
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_gear.1.prop3_ab_core_max.smt2	2.5 s	1.3 s	+85.32%
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_gear.1.prop4_ab_core_max.smt2	1,330.6 ms	959.6 ms	+38.67%
👁	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_lamport.3.prop1_ab_min_max.smt2	290.7 ms	329.5 ms	-11.77%
👁	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_leader_election.2.prop1_ab_min_max.smt2	702.9 ms	871.7 ms	-19.36%
👁	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_leader_election.5.prop1_ab_min_max.smt2	813.4 ms	1,020.7 ms	-20.31%
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_msmie.4.prop1_ab_core_max.smt2	1.8 s	1 s	+82.39%
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_pgm_protocol.2.prop1_ab_core_max.smt2	2.1 s	1.1 s	+95.84%
👁	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_pgm_protocol.7.prop5_ab_min_max.smt2	525 ms	657.7 ms	-20.17%
👁	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_pgm_protocol.8.prop1_ab_min_max.smt2	955.8 ms	1,221.5 ms	-21.76%
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_plc.4.prop2_ab_core_max.smt2	20.5 s	1.6 s	×13
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_rether.2.prop1_ab_core_max.smt2	1,012.5 ms	390.3 ms	×2.6
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_telephony.1.prop1_ab_core_max.smt2	1,018.9 ms	608.5 ms	+67.45%
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_telephony.7.prop1_ab_core_max.smt2	2.7 s	1.2 s	×2.2
⚡	benches/starexec/incremental/QF_UF/2018-Goel-hwbench/QF_UF_train-gate.5.prop1_ab_core_max.smt2	711.3 ms	458.2 ms	+55.24%