[NI] Remove Nothing result type restriction in most cases

Make Nothing as result type not suitable only for if, when, try and ?: special functions.

compiler/testData/diagnostics/tests/controlFlowAnalysis/throwInLambda.fir.kt

@@ -1,4 +1,3 @@
-// !WITH_NEW_INFERENCE
 // See KT-10913 Bogus unreachable code warning
 
 fun fn() : String? = null

compiler/testData/diagnostics/tests/controlFlowAnalysis/throwInLambda.kt

@@ -1,4 +1,3 @@
-// !WITH_NEW_INFERENCE
 // See KT-10913 Bogus unreachable code warning
 
 fun fn() : String? = null
@@ -8,6 +7,6 @@ fun foo(): String {
 }
 fun bar(): String {
     val x = fn() ?: return ""
-    <!UNREACHABLE_CODE!>val <!UNUSED_VARIABLE!>y<!> =<!> x<!UNNECESSARY_SAFE_CALL!>?.<!>let { throw Exception() } <!NI;UNREACHABLE_CODE, NI;USELESS_ELVIS, OI;UNREACHABLE_CODE, OI;USELESS_ELVIS!>?: "unreachable"<!>
+    <!UNREACHABLE_CODE!>val <!UNUSED_VARIABLE!>y<!> =<!> x<!UNNECESSARY_SAFE_CALL!>?.<!>let { throw Exception() } <!UNREACHABLE_CODE, USELESS_ELVIS!>?: "unreachable"<!>
     <!UNREACHABLE_CODE!>return y<!>
 }