Update default page scan parameters

Set BTM_DEFAULT_CONN_WINDOW/INTERVAL from 11.25ms/1280ms to
11.25ms/640ms which is a known sweet spot.

Test: check new page scan parameters
Bug: 196815018
Tag: #refactor
Ignore-AOSP-First: Already merged in AOSP
Merged-In: I730b12b44dbb0c36a5dc4e4984cc1920b7c1c490
Change-Id: Iac87c23625f5fdf7b66a3e96c98f2be49c482fae