Hearing Aid: codec and connection interval switching

Added support to switch the LE Connection Interval between 10 msec and
20 msec. Uses the "persist.bluetooth.hearingaid.interval" to configure.

Test: Manually use hearing aid devices and switches between 10 msec and
20 msec connection interval
Bug: 79579786

Change-Id: Iec15a0c9f76afe265368fd90662ffe60a29fb27b