drm_hwcomposer: CI: Use aospext to provide headers for clang-tidy
Since we're now using aospless archive for meson.build, we can use headers from there and remove .ci/android_headers/ directory completely.
Adding aospless cflags also raised some new tidy checks fails, which were fixed by this commit.
Since clang-tidy now relies on aospless files, running CI on the host can't be supported and removed. Running CI within the docker container is the only option left.