Nielsen optimizations

[vhavlena]

This PR optimizes the Nielsen transformation with a priority queue instead of dequeue as a datastructure for storing nodes of a proof graph. Now we prefer nodes with smaller formulae as they more likely reach a final node.

[vhavlena]

Results on everything

# of formulae: 103318
--------------------------------------------------
tool                                               ✅     ❌       time    avg    med    std    sat    unsat    unknown     TO    MO+ERR    other
-----------------------------------------------  ----  -----  ---------  -----  -----  -----  -----  -------  ---------  -----  --------  -------
z3-noodler-605ccd5-d95fe13                          0   1342   15990.37   0.16   0.01   1.75      0        0        638    658        46        0
z3-noodler-b0899c4-d95fe13                          0   1365   16198.75   0.16   0.02   1.75      0        0        638    658        69        0
cvc5-1.1.2                                          0   3619   76478.24   0.77   0.00   6.77      0        0          2   3608         9        0
z3-4.13.0                                           0   5631  132036.99   1.35   0.01   8.11      0        0        210   4960       461        0
ostrich-5dd2e10ca                                   0  16986  782639.00   9.06   1.75  19.20      0        0          0  16962        12       12
z3-4.13.0+cvc5-1.1.2                                0   2562   60604.78   0.60   0.00   6.00      0        0       2562      0         0        0
z3-noodler-605ccd5-d95fe13+z3-4.13.0+cvc5-1.1.2     0    144   11050.73   0.11   0.00   1.61      0        0        144      0         0        0
--------------------------------------------------

Results on woorpje (targetted benchmark)

Benchmark woorpje
# of formulae: 809
--------------------------------------------------
tool                                               ✅    ❌     time    avg    med    std    sat    unsat    unknown    TO    MO+ERR    other
-----------------------------------------------  ----  ----  -------  -----  -----  -----  -----  -------  ---------  ----  --------  -------
z3-noodler-605ccd5-d95fe13                          0    36   144.39   0.19   0.01   1.70      0        0          0    19        17        0
z3-noodler-b0899c4-d95fe13                          0    59   296.91   0.40   0.02   2.62      0        0          0    19        40        0
cvc5-1.1.2                                          0    54    45.21   0.06   0.01   0.23      0        0          0    54         0        0
z3-4.13.0                                           0    27   300.36   0.38   0.02   4.80      0        0          0    27         0        0
ostrich-5dd2e10ca                                   0    55  7072.39   9.36   4.64  15.95      0        0          0    51         2        2
z3-4.13.0+cvc5-1.1.2                                0    20    67.20   0.09   0.01   0.89      0        0         20     0         0        0
z3-noodler-605ccd5-d95fe13+z3-4.13.0+cvc5-1.1.2     0    11    42.57   0.05   0.01   0.84      0        0         11     0         0        0
--------------------------------------------------

[jurajsic]

Looks good.

[vhavlena]

Can I merge it?