Tyche logging support

[vasumv]

Resolves #257

Logging support for Tyche (feature flag enabled by -DjqfObservability). The output file will be target/fuzz-results/TEST_CLASS/TEST_METHOD/observations.jsonl. The output file can then be uploaded to
https://tyche-pbt.github.io/tyche-extension/

Modifies FuzzStatement to add logging at the end of the guidance loop if the flag is enabled. Adds the fuzz.util.Observability.event method that can be invoked in the fuzz target to log specific input features. Per-input coverage still not yet implemented. Since the coverage data in Tyche is per-input line coverage for each file, this should be done as a post processing step.

Example fuzz target (for ChocoPy):

@Fuzz
public void fuzzSemanticAnalysis(@From(ChocoPySemanticGenerator.class) String code) {
    Program program = RefParser.process(code, false);
    assumeTrue(!program.hasErrors());
    event("numStatements", program.statements.size());
    event("numDeclarations", program.declarations.size());
    Program typedProgram = RefAnalysis.process(program);
    event("numErrors", program.getErrorList().size());
    assumeTrue(!typedProgram.hasErrors());
}

Example visualization:

[rohanpadhye]

LGTM, thanks!