tests/heapalloc_*: Refactor some tests to work in strict stackless mode.

In strict stackless mode, it's not possible to make a function call with
heap locked (because function activation record aka frame is allocated on
heap). So, if the only purpose of function is to introduce local variable
scope, move heap lock/unlock calls inside the function.

tests/micropython/heapalloc_exc_raise.py

@@ -5,6 +5,7 @@ import micropython
 e = ValueError("error")
 
 def func():
+    micropython.heap_lock()
     try:
         # This works as is because traceback is not allocated
         # if not possible (heap is locked, no memory). If heap
@@ -16,8 +17,7 @@ def func():
         raise e
     except Exception as e2:
         print(e2)
+    micropython.heap_unlock()
 
-micropython.heap_lock()
 func()
 print("ok")
-micropython.heap_unlock()

tests/micropython/heapalloc_iter.py

@@ -11,8 +11,10 @@ except (ImportError, AttributeError):
     heap_lock = heap_unlock = lambda:0
 
 def do_iter(l):
+    heap_lock()
     for i in l:
         print(i)
+    heap_unlock()
 
 def gen_func():
     yield 1
@@ -55,7 +57,6 @@ print(sum(t))
 heap_unlock()
 
 # test iterating over collections with the heap locked
-heap_lock()
 do_iter(b'123')
 do_iter(ba)
 do_iter(ar)
@@ -66,4 +67,3 @@ do_iter(s)
 do_iter(fs)
 do_iter(g1)
 do_iter(g2)
-heap_unlock()

tests/micropython/heapalloc_traceback.py

@@ -16,17 +16,17 @@ except:
     pass
 
 def test():
+    micropython.heap_lock()
     global global_exc
     global_exc.__traceback__ = None
     try:
         raise global_exc
     except StopIteration:
         print('StopIteration')
+    micropython.heap_unlock()
 
 # call test() with heap allocation disabled
-micropython.heap_lock()
 test()
-micropython.heap_unlock()
 
 # print the exception that was raised
 buf = uio.StringIO()

tests/micropython/heapalloc_traceback.py.exp

@@ -1,5 +1,5 @@
 StopIteration
 Traceback (most recent call last):
-  File  , line 22, in test
+  File  , line 23, in test
 StopIteration: