Refactoring: Decouple API implementation from config structures

[madmike200590]

The aim of this PR is to get rid of all dependencies between SystemConfig and API implementations (like AlphaImpl, NaiveGrounder, DefaultSolver etc). The idea is that these objects should get their dependencies at the time of construction from an external source (AlphaFactory as it is implemented now) and not need to be aware of any configuration mechanisms or structures themselves.

The same mechanism of obtaining Alpha instances (only through AlphaFactory) has been applied to all tests that test complete workflows (i.e. tests constituting end-to-end-tests in that they test the complete system rather than a single unit of code) as well. These tests (everything annotated RegressionTest or AggregateRegressionTest) have been moved to the alpha-solver module and adapted to be parameterized using a SystemConfig which is used to obtain an Alpha instance from the factory.

Additional changes:

• renamed ASPCore2Program to InputProgram
• removed config option for grounder name; it doesn't seem realistic that we get an alternative implementation in the short- or mid-term that would make such an option necessary
• removed "deterministic" CLI option - instead select a seed directly
• pulled code used in tests across multiple modules into separate source folder alpha-core/src/testFixtures that can be shared between modules
• fix minor bug in StratifiedEvaluation: Avoid generating duplicate facts by using a Set rather than List as intermediate storage for newly derived rule heads

[codecov[bot]]

Codecov Report

Merging #336 (1b04d74) into refactor-tests (515949e) will decrease coverage by 32.76%. The diff coverage is 34.24%.

@@                  Coverage Diff                  @@
##             refactor-tests     #336       +/-   ##
=====================================================
- Coverage             71.11%   38.35%   -32.77%     
+ Complexity             2167     1200      -967     
=====================================================
  Files                   182      185        +3     
  Lines                  8033     8073       +40     
  Branches               1424     1422        -2     
=====================================================
- Hits                   5713     3096     -2617     
- Misses                 1938     4639     +2701     
+ Partials                382      338       -44     

Impacted Files	Coverage Δ
.../tuwien/kr/alpha/app/config/CommandLineParser.java	82.47% <ø> (-0.42%)	:arrow_down:
...tuwien/kr/alpha/core/grounder/GrounderFactory.java	0.00% <0.00%> (-50.00%)	:arrow_down:
...c/tuwien/kr/alpha/core/grounder/NaiveGrounder.java	45.38% <0.00%> (-35.19%)	:arrow_down:
...tuwien/kr/alpha/core/parser/ProgramParserImpl.java	65.30% <0.00%> (-12.25%)	:arrow_down:
...wien/kr/alpha/core/programs/NormalProgramImpl.java	100.00% <ø> (ø)
.../at/ac/tuwien/kr/alpha/core/programs/Programs.java	0.00% <ø> (-50.00%)	:arrow_down:
.../programs/transformation/EnumerationRewriting.java	0.00% <0.00%> (-85.72%)	:arrow_down:
...transformation/NormalizeProgramTransformation.java	0.00% <0.00%> (-100.00%)	:arrow_down:
...programs/transformation/PredicateInternalizer.java	0.00% <0.00%> (-74.20%)	:arrow_down:
.../programs/transformation/StratifiedEvaluation.java	0.00% <0.00%> (-97.80%)	:arrow_down:
... and 110 more

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