Add support for PEP 770 (SBOMs)

Add an `--sbom` option to `sip-wheel` (and other build tools as appropriate) that can be specified multiple times to identify the names of files and directories that will be copied to the `sboms` subdirectory of the `dist-info` directory as described in [PEP 770](https://peps.python.org/pep-0770/).