Add modem logs to the bugreport

When user takes bug report, collect modem logs and add it to the
bugreport zip file.

Test: Take Bugreport and ensure that the modem logs are present
in userdebug builds. Also check that bug reports are collected
normally if there are no modem logs.

BUG=32219165

Change-Id: Ia20fc95ceee95972e17ac4193d350bbae36b3630