py/runtime: Move mp_exc_recursion_depth to runtime and rename to raise.

For consistency this helper function is renamed to match the other
exception helpers, and moved to their location in runtime.c.
diff --git a/py/runtime.h b/py/runtime.h
index 3f0d110..a19f64c 100644
--- a/py/runtime.h
+++ b/py/runtime.h
@@ -151,7 +151,7 @@
 NORETURN void mp_raise_TypeError(const char *msg);
 NORETURN void mp_raise_NotImplementedError(const char *msg);
 NORETURN void mp_raise_OSError(int errno_);
-NORETURN void mp_exc_recursion_depth(void);
+NORETURN void mp_raise_recursion_depth(void);
 
 #if MICROPY_BUILTIN_METHOD_CHECK_SELF_ARG
 #undef mp_check_self