Bluetooth: shell: GATT: Make get command take a handle range

This enables get command to operate on a handle range so multiple
attributes values can be printed out:

uart:~$ gatt get 0x0001 0xffff
attr 0x00506600 uuid 2800 perm 0x01
00000000: 01 18
attr 0x00506600 uuid 2803 perm 0x01
00000000: 20 03 00 05 2A
attr 0x00506600 uuid 2a05 perm 0x00
attr 0x00506600 uuid 2902 perm 0x03
00000000: 00 00
attr 0x00506600 uuid 2803 perm 0x01
00000000: 0A 06 00 29 2B
attr 0x00506600 uuid 2b29 perm 0x03
00000000: 00
attr 0x00506600 uuid 2803 perm 0x01
00000000: 02 08 00 2A 2B
attr 0x00506600 uuid 2b2a perm 0x01
00000000: AA 2D 05 EB E8 1D D0 E5 F7 B9 C1 B6 3F 66 93 15
attr 0x00506600 uuid 2800 perm 0x01
00000000: 00 18
attr 0x00506600 uuid 2803 perm 0x01
00000000: 0A 0B 00 00 2A
attr 0x00506600 uuid 2a00 perm 0x09
00000000: 74 65 73 74 20 73 68 65 6C 6C
attr 0x00506600 uuid 2803 perm 0x01
00000000: 02 0D 00 01 2A
attr 0x00506600 uuid 2a01 perm 0x01
00000000: 00 00
attr 0x00506600 uuid 2803 perm 0x01
00000000: 02 0F 00 A6 2A
attr 0x00506600 uuid 2aa6 perm 0x01
00000000: 01
attr 0x00506600 uuid 2803 perm 0x01
00000000: 02 11 00 04 2A
attr 0x00506600 uuid 2a04 perm 0x01
00000000: 18 00 28 00 00 00 2A 00
attr 0x00506600 uuid 2800 perm 0x01
00000000: 0D 18
attr 0x00506600 uuid 2803 perm 0x01
00000000: 10 14 00 37 2A
attr 0x00506600 uuid 2a37 perm 0x00
attr 0x00506600 uuid 2902 perm 0x03
00000000: 00 00
attr 0x00506600 uuid 2803 perm 0x01
00000000: 02 17 00 38 2A
attr 0x00506600 uuid 2a38 perm 0x01
00000000: 00
attr 0x00506600 uuid 2803 perm 0x01
00000000: 08 19 00 39 2A
attr 0x00506600 uuid 2a39 perm 0x00

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>