When installing plugins from remote sources, either the Elastic download
service, or maven, a checksum file is downloaded and checked against the
downloaded zip. The current format for official plugins is to use a
sha512 checksum which includes the zip filename. This format matches
that from sha512sum, and allows using the --check argument there to
verify the checksum manually. However, when generating checksum files
with maven and gradle, the filename is not included.
This commit relaxes the requirement the filename existing within the
sha512 checksum file for maven plugins. We continue to strictly enforce
official plugins have the existing format of the file.
closes#52413
a1e7429ccc