wamr-python: Enable debugging WASM and grant dir access (#2449)

- Enable debugging a WASM loaded and executed from Python.
- Expose API to enable access to list of host directories. Similar to --dir in iwasm.
- Add another python language binding sample: native-symbol.

language-bindings/python/wamr-api/samples/native-symbol/func.c

@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include <stdio.h>
+
+int
+python_func(int val);
+
+int
+add(int val1, int val2)
+{
+    return val1 + val2;
+}
+
+int
+c_func(int val)
+{
+    printf("c: in c_func with input: %d\n", val);
+    printf("c: calling python_func(%d)\n", val + 1);
+    int res = python_func(val + 1);
+    printf("c: result from python_func: %d\n", res);
+    printf("c: returning %d\n", res + 1);
+    return res + 1;
+}
+
+int
+main()
+{}