Allow ARP wildcard matching at the start of the attribute values

Currenty, we only support matching of attribute values with wildcards at the end of the string: https://github.com/OpenConext/OpenConext-engineblock/blob/b64cea9e6350b1884ea9618f4a765c258225633c/src/OpenConext/EngineBlock/Metadata/AttributeReleasePolicy.php#L204-L216

This works well for urns etc (such as in eduPersonEntitlement) but not in email-syntax values like mail and eduPersonPrincipalName. However, sometimes it is useful to only release ePPN or mail for a specific institution. See for example https://servicedesk.surf.nl/jira/browse/SD-129817

So I would like to add support for suffix-matching, for example to be able to release ePPN and mail only for *@uni-harderwijk.nl. Looking at the code (linked above) this seems rather straightforward.

Note that I explicitly do not whish to introduce support for wildcards in the middle of the string

Start in src/OpenConext/EngineBlock/Metadata/AttributeReleasePolicy.php around lines 204-216, where attribute-value wildcard matching is implemented. Trace the existing end-of-string matching behavior and identify the relevant test coverage, then verify that suffix matching such as *@uni-harderwijk.nl works while wildcards in the middle remain unsupported.