SYNTHESIZER: Add dump-loop-contracts into loop-contracts synthesizer

[qinheping]

Running the loop-contracts synthesizer with the flag dump-loop-contracts will output the synthesized contracts as a JSON file, which can be used to annotate back to the source code with Crangler.

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[jimgrundy]

I'm ok with the changes to the synthesizer, but the changes to c_wranger and the expression type not so much. They do look like improvements/fixes, but they should be factored into their own PRs so they and their consequences can be evaluated without holding up the synthesizer change.

Do please make those other PRs though.

[tautschnig]

With all other PRs now merged: can you use expr2c with a custom configuration that sets up true and false as you initially did in the default configuration? I believe this will (after a rebase) make all tests pass.

[codecov]

Codecov Report

Base: 78.47% // Head: 78.48% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (531e768) compared to base (954df79).
Patch coverage: 91.13% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #7451   +/-   ##
========================================
  Coverage    78.47%   78.48%           
========================================
  Files         1662     1663    +1     
  Lines       191045   191112   +67     
========================================
+ Hits        149931   149992   +61     
- Misses       41114    41120    +6     

Impacted Files	Coverage Δ
.../goto-synthesizer/goto_synthesizer_parse_options.h	100.00% <ø> (ø)
...oto-synthesizer/goto_synthesizer_parse_options.cpp	66.66% <73.07%> (-1.34%)	⬇️
src/goto-synthesizer/dump_loop_contracts.cpp	100.00% <100.00%> (ø)
...hesizer/enumerative_loop_contracts_synthesizer.cpp	92.43% <100.00%> (ø)

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