2/2 analysis-api: Initial implementation for contracts

Review: https://jetbrains.team/p/kt/reviews/7652

Put this change into a separate commit because:
1. The change is boring and clutters the diff of the first commit
2. The first commits is already too big

analysis/analysis-api/testData/scopes/fileScopeTest/simpleFileScope.txt

@@ -13,6 +13,7 @@ KtFunctionSymbol:
   annotationsList: []
   callableIdIfNonLocal: /test
   contextReceivers: []
+  contractEffects: []
   hasStableParameterNames: true
   isBuiltinFunctionInvoke: false
   isExtension: false