tests/micropython: Test loading const objs in native and viper funcs.

tests/micropython/native_const.py

+# test loading constants in native functions
+
+@micropython.native
+def f():
+    return b'bytes'
+print(f())
+
+@micropython.native
+def f():
+    @micropython.native
+    def g():
+        return 123
+    return g
+print(f()())

tests/micropython/native_const.py.exp

+b'bytes'
+123

tests/micropython/viper_const.py

+# test loading constants in viper functions
+
+@micropython.viper
+def f():
+    return b'bytes'
+print(f())
+
+@micropython.viper
+def f():
+    @micropython.viper
+    def g() -> int:
+        return 123
+    return g
+print(f()())

tests/micropython/viper_const.py.exp

+b'bytes'
+123

tests/micropython/viper_const_intbig.py

+# check loading constants
+
+@micropython.viper
+def f():
+    return 123456789012345678901234567890
+
+print(f())

tests/micropython/viper_const_intbig.py.exp

+123456789012345678901234567890