InputVerifier: Accept invalid utf-8 strings silently

Rust's String seems to have more strict requirements than cpp's
std::string, since its creation will fail if the string is not valid in
its encoding format. rust::String from cxxbridge escalates the error
and causes a panic.

Since we do not perform a validity check on the std::string that comes
from apps, we must use rust::String::lossy() to create the rust::String
for cxxbridge, since it is tolorant of invalid encodings.

Bug: 295014987
Test: atest libinput_tests
Change-Id: I45ecc6117a43cf25ac6ac15fd57ae25e7174d88f