Add Extended Advertise Support.

Implement the following APIs in the porting layer:

• bt_le_ext_adv_update_param
• bt_le_ext_adv_set_data
• bt_le_ext_adv_start
• bt_le_ext_adv_stop
• bt_le_ext_adv_create

When AE is used, the user can use its capability to send large payload without segmentation

To use the AE large data sending, increase the size of a mesh msg segment to 226 bytes when AE is used (which is the max possible size to send without using BLE segmentation).

Why the size is 226?

1. The size of an AE packet is 255 bytes.
2. The advertise header size is 2 bytes.
3. The extended header size is 9 bytes.
4. The Mesh network header + NetMIC size is 9 + 4 bytes.
5. The lower transport layer header size is 4 bytes.
6. After reducing 2-5 from the AE packet size, we have 226 bytes left for Mesh msg data.