Change Service Tasks labels to Custom Tasks

We need to sync the naming of previously called `Service Tasks` to `Custom Tasks` across the business-central.

This is a follow-up after the changes being made in process designer (see RHPAM-3008).

The details of changes needed are in attached screenshots.

Acceptance criteria

Service tasks are changed to Custom Tasks in business-central in:

• Project -> Settings -> Service Tasks
• Administration -> Custom Tasks Administration