Fastboot: Add new TEXT message to protocol to handle long lines.

Trusty Benchmarks need to be evaluated in ABL which is much more
controlled than linux. However fastboot prints evry atomic message from
trusty/abl on its own line starting with "(bootloader)"

Bug: 263454481
Test: - "fastboot oem trusty runtest trusty.hwrng.bench"
Change-Id: I99847a8cc54457c8ec809e219736325dce0ac891