AZC0003: Analyzer should flag missing virtual keyword for any service methods

Currently the check is restricted to types with a "Client" suffix. We would ideally flag any public async method (and its sync variant) if it is not virtual.

The issue names the AZC0003 analyzer but no source file or test entry point. Start by locating the analyzer and the existing check for types ending in "Client", then inspect its tests if present. Done means public async service methods and their sync variants are flagged when they are not virtual, without restricting the check to Client-suffixed types.

Written by the indexing model from the issue text.