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/symbols/symbolByPsi/contextReceivers/contextReceiversOnFunction.txt

@@ -5,6 +5,7 @@ KtFunctionSymbol:
     ContextReceiver(kotlin/Int)
     ContextReceiver(s@kotlin/String)
   ]
+  contractEffects: []
   hasStableParameterNames: true
   isBuiltinFunctionInvoke: false
   isExtension: false