scripts: zspdx: scanner: load REUSE.toml, surface its licenses

get_copyright_info() built its REUSE Project with the bare Project()
constructor, which never loads REUSE.toml - only
Project.from_directory() does, so bulk licensing data was never read.

Build one Project.from_directory(component.base_dir) per component.
Rename get_copyright_info() to get_reuse_info(), also returning
license expressions used in scan_sbom_graph() when a file has no
in-file SPDX-License-Identifier tag, and quiet the reuse library's
logger to avoid noise from newly-surfaced compliance warnings.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>
Assisted-by: Claude:sonnet-5