feat: containing/containedIn/intersecting joiners

[triceo]

Replaces #972.

[Copilot]

Pull request overview

This PR refactors constraint providers to use new specialized joiner methods (containing, containedIn, intersecting) instead of generic filtering joiners, replacing PR #972. The changes improve code readability and leverage Timefold's optimized joiner implementations.

Changes:

• Replaced filtering with Joiners.intersecting for set intersection checks
• Replaced filtering with Joiners.containing and containedIn for containment checks
• Removed obsolete helper methods from Talk class that are no longer needed
• Reorganized imports for better structure

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
java/maintenance-scheduling/src/main/java/org/acme/maintenancescheduling/solver/MaintenanceScheduleConstraintProvider.java	Replaced filtering with Joiners.intersecting for tag conflict detection; reorganized imports
java/conference-scheduling/src/main/java/org/acme/conferencescheduling/solver/ConferenceSchedulingConstraintProvider.java	Replaced multiple filtering joiners with specialized joiners (containing, containedIn, intersecting) across 13 constraints; reorganized imports
java/conference-scheduling/src/main/java/org/acme/conferencescheduling/domain/Talk.java	Removed helper methods hasSpeaker, hasMutualSpeaker, and overlapsTime that are no longer needed after joiner refactoring; reorganized imports

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[TomCools]

LGTM