Bump GATT cache file version marker

In commit 2238a88f, the type used for UUID in the GATT cache was changed
from tBT_UUID to bluetooth:Uuid. This changed the binary representation of
this field. 18 bytes were used previously, now only 16 bytes are used.
This change made GATT cache file format incompatible between Android
versions, and requires an increment of cache file format version.

Fixes: 70297056
Test: added GattCacheTest
Change-Id: I4bceada300dbe3aab10d14df2aa853e4573c536e