Run some inputflinger_tests on host

Sometimes, it's convenient to execute the input tests without having a
connected device. This is especially useful when doing cherry-picks of
patch on a cloud device.

Allow input code to build for host, and enable the tests for running on
host.

Bug: 249591924
Test: atest --host --no-bazel-mode -c -m inputflinger_tests
Change-Id: Ib9be6a5fb6c35ffc450e41cb2a5688bfb2c8d01a