[19.0][MIG] hr_expense_trip: Migration to 19.0

[dnplkndll]

Port of hr_expense_trip to 19.0.

Non-mechanical adaptations worth flagging

• Sheetless Trip Grouping: Refactored the module to link individual hr.expense lines directly to a new hr.expense.trip model, completely bypassing the removed hr.expense.sheet core model.
• Trip Field Integration: Automatically maps and links individual expense lines with the newly defined trip model, with consistent constraints on date ranges and employees.
• WIP Completion: Completed the active implementation based on the upstream PR [19.0][WIP][ADD] hr_expense_trip: Link expenses with trips #337 work.

[dnplkndll]

Closing PR as it was accidentally opened from a personal fork instead of the ledoent organization.