Disallow connect with Secure Connections downgrade

As a guard against the BLUFFS attack, check security parameters of
incoming connections against cached values and disallow connection if
these parameters are downgraded or changed from their cached values.

This CL adds the connection-time check for Secure Connections mode.

Bug: 314331379
Test: m libbluetooth
Test: manual

To test this CL, please ensure that BR/EDR initial connections and reconnections  (after cycling remote devices, cycling Bluetooth, restarting the phone, etc.) work against remote devices which both support and do not support Secure Connections mode, and with all supported bonding types.  Basic validation of LE bonding functionality should be done as well.

Tag: #security
Ignore-AOSP-First: Security
Change-Id: I874a606a8e61006651dfb0932365b1aea248c100