Revert "base: App crash when select suggestion's length more than specified."

This reverts commit 95830e545d7af2fe469db5e151d303d5ea198e70.
Revert "Handle backup transport registration dynamically"

This reverts commit cefba58d14f9669b57c16b4ea493779d882c43bd.
Revert "Harden against transiently unavailable backup transports"

This reverts commit 28b6d3829166935f50684c0152a154cd4f1bbb90.