Refactor: improve maintainability

[karoliineh]

Tests refactoring:

• Move method mockGoblintServerIsAlive that is used in several Test classes to a new TestHelper class 60b433e
• Inline initializing gsonBuilder from a dedicated method to class field 60b433e
• Generalize readGoblintMessagesResponseJson and readGoblintFunctionsResponseJson to one function 60b433e
• Move duplicated code fragments to a BeforeEach method in GoblintAnalysisTest 60b433e

Source refactoring:

• Convert GobPieConfiguration class to a record 4a66bc3 1bdbec7
• Convert GoblintFunctionsResult class to a record bbe19ec
• Convert GoblintAnalysisResult class to a record 90aaf5a
• Remove unused imports from several files b5370d2
• Remove unused getter getType from GobPieException 84e9f4f

Improvements in tests:

• Improve abortAnalysis assertions 60b433e
• Add tests for Goblint responding with statuses Aborted or VerifyError bbe19ec
• Change a test to cover a use case where analysis is called with incrementalAnalysis set to false 9977cdf