[FIR] Improve the control flow graph around try expressions

1. throw goes to catches instead of main exist block
2. return goes via finally (single level only supported atm)
3. collect non-direct return to retrieve all return expressions easier

compiler/testData/codegen/boxInline/complexStack/spillConstructorArgumentsAndInlineLambdaParameter.kt

@@ -1,4 +1,3 @@
-// IGNORE_FIR_DIAGNOSTICS
 // FILE: 1.kt
 class A(val s: String)