gatt-client : Simplify service / characteristic discovery

gatt-client : Simplify service / characteristic discovery

[Problem] N/A
[Cause & Measure] Simplify service / characteristic discovery
[Checking Method] Make GATT connection

. When remote device has 41 attributes
  - Before patch : 5.431658167 secs
  - After patch : 3.921924167 secs

. Below upstream commits are imported by this patch.

commit a39cd38a3db73b1d2d78370b7c678ac47f560c13
Author: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Date:   Tue May 9 12:59:16 2017 +0300
    shared/gatt-client: Simplify characteristics discovery

commit 82c7e0365702e343d6dad0baa23bdff59be27b0c
Author: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Date:   Tue May 9 12:47:40 2017 +0300
    shared/gatt-db: Add gatt_db_insert_descriptor

commit 87abac457f4e2037c2cd6e4f30384e2ab4fa662b
Author: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Date:   Mon May 8 20:18:25 2017 +0300
    shared/gatt-db: Add gatt_db_insert_characteristic

commit f78146f96fb254e43d3d003ddcdf97983cf764f1
Author: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Date:   Mon May 8 16:52:05 2017 +0300
    shared/gatt-client: Simplify included discovery

commit 0c9f030b1b3c8cf96feb9f702c5b925a1dc9ea69
Author: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Date:   Mon May 8 16:00:46 2017 +0300
    shared/gatt-db: Add gatt_db_insert_included

commit 7aaa6c893aa89a61d20460e1ab89ac419435c3a1
Author: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Date:   Mon May 8 15:48:02 2017 +0300
    shared/gatt-client: Insert included attribute with handle

commit 108336ee3e68f3e71b2229aee83a7d03e0cde618
Author: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Date:   Mon May 8 15:33:26 2017 +0300
    shared/gatt-db: Add gatt_db_service_insert_included

commit ba07a8bfc07a744081b3d7df51803cad9062aa8c
Author: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Date:   Mon May 8 13:46:30 2017 +0300
    shared/gatt-db: Add gatt_db_get_service

Change-Id: I1bd68ff4a498ae3da56225533df31ec18221ffde