Fix Issue #10022. (#10587)

Fix Issue #10022. (#10587)

This issue occurred because the JIT currently inserts the P/Invoke
method prolog into the first block of a function without ensuring that
this block will only execute once. This is not safe, as executing the
P/Invoke prolog multiple times can create cycles in the frame list and
casue the stack unwinder to hang.

This change ensures that lowering inserts a new, single-entry basic
block at the beginning of the function for functions that require P/Invoke prologs.