[Odometer] Create NewDot Odometer expense flow

[Julesssss]

Odometer Project implementation Phase 1

Tracking issue

Part of the Add Odometer mileage to NewDot project (design doc)

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Task

Implement these changes from the Odometer design doc:

• Add an Odometer tab to the Distance Request Start page
• Create Odometer expense page
• Add error handling for completed expenses
• Reuse Discard Changes modal when user exits flow
• Calculate total distance when both readings exist
• Add total mileage field to Confirm Details page

[Julesssss]

PR in progress