[FIR IDE] Ensure resolve to CONTRACTS phase in ReturnTypeCalculator

If we want to analyse some function's call, we need to know about its
contracts, otherwise resolving the following code would be broken.
Computing return type of function is a prerequisite to using it in any
sensible way, so it's the best place to resolve it to CONTRACTS

KT-50733

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/useBeforeDeclaration.fir.kt

@@ -1,4 +1,3 @@
-// FIR_IDE_IGNORE
 // !LANGUAGE: +AllowContractsForCustomFunctions +UseReturnsEffect
 // !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
 // !OPT_IN: kotlin.contracts.ExperimentalContracts

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/useBeforeDeclaration.kt

@@ -1,4 +1,3 @@
-// FIR_IDE_IGNORE
 // !LANGUAGE: +AllowContractsForCustomFunctions +UseReturnsEffect
 // !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
 // !OPT_IN: kotlin.contracts.ExperimentalContracts