CaloTrackingGeometryBuilder: remove remaining mutables

• Make local copies of property values to avoid mutable. Modifying property values is bad to begin with.
• Make bpCutouts a local variable and pass it explicitly
• protect garbage bin with mutex and mark thread-safe

Once the trackingGeometry() interface is declare thread-safe, this class should pass the thread-checker.

Relates to ATLASRECTS-7252.