OPP: Fix ANR during retry failed transfer

Use Case:
1. Open Video from G photos App
2. Select large (above 50 MB )  video and share via Bluetooth.
3. while transfer is in progress, stop sending the video.
4. The video will come under "outbound transfers" in the DUT .
5. Select the video again from the "outbound transfers" & tap on "try again" , Observe

Failure:
Observed ANR in OPP profile.

Root Cause:
BluetoothOppSendFileInfo::generateFileInfo() takes long time to process
when sharing file from G photos app.

Fix:
When tap the "try again" button on the send failed dialog, the
method "BluetoothOppSendFileInfo::generateFileInfo()" will be
call, this method would be very time consuming , thereby causing ANR.
Changed this method into the child thread execution to avoid ANR in BT context.

Fixes: 141833952
Test: Perfomed above use case issue not seen.
Change-Id: Ie50771d7b5cdd1e0dd47834996135f2ea8e03a5c