Allow partial analysis for CallGraphAlgorithm

[Liyw979]

#710
This PR cleans up usage of superClassesOf and getClassOrThrow.

Tested with

  public static void main(String[] args) {

    AnalysisInputLocation<JavaSootClass> inputLocation = PathBasedAnalysisInputLocation.create(
            Paths.get("hutool-db-5.7.18.jar"), SourceType.Application);

    JavaLanguage language = new JavaLanguage(8);

    JavaProject project = JavaProject.builder(language).addInputLocation(inputLocation).build();
    JavaView view = project.createView();
    AbstractCallGraphAlgorithm cha = new ClassHierarchyAnalysisAlgorithm(view);
    Stream<MethodSignature> methods = view.getClasses()
            .stream()
            .flatMap(c -> c.getMethods().stream())
            .map(SootClassMember::getSignature);
    CallGraph graph = cha.initialize(methods.collect(Collectors.toList()));
    System.out.println(graph);
  }

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (5140a36) 64.90% compared to head (74da0de) 64.90%.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #711   +/-   ##
==========================================
  Coverage      64.90%   64.90%           
+ Complexity      3368     3367    -1     
==========================================
  Files            313      313           
  Lines          14960    14960           
  Branches        2525     2524    -1     
==========================================
  Hits            9710     9710           
  Misses          4351     4351           
  Partials         899      899           

Files	Coverage Δ
...a/sootup/callgraph/AbstractCallGraphAlgorithm.java	89.63% <100.00%> (+0.12%)	⬆️
...src/main/java/sootup/java/core/views/JavaView.java	90.38% <100.00%> (-0.36%)	⬇️
.../java/sootup/core/typehierarchy/TypeHierarchy.java	80.64% <0.00%> (ø)

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[swissiety]

looks good 👍