[FIR] Make sure the primary constructor is first in class CFG

The primary constructor of a class needs to be the first subgraph of the
class control-flow graph. Based on the Kotlin specification, class
initialization order goes first primary constructor, in-place
declarations (properties and init blocks), and then secondary
constructors. If the class doesn't have a primary constructor, then it
is just skipped in the order.

Unfortunately, the class control-flow graph had in-place declarations
first and then all constructors. Instead, we should treat the primary
constructor as the first in-place declaration, and then continue with
the existing processing as secondary constructors. This will guarantee
that super constructor calls have the correct property initialization
information.

^KT-65093 Fixed

compiler/testData/diagnostics/tests/initializedAfterRethrow.kt

@@ -1,3 +1,5 @@
+// FIR_IDENTICAL
+
 fun foo(): Int = 42
 
 object ThrowInTryWithCatch {