feat(fms): compute capture condition in fms

[BlueberryKing]

Fixes #[issue_no]

Summary of Changes

Implement the computation of the NAV capture zone in the flight management system. Previously, NAV mode would engage whenever it was armed and XTE < 1NM. Now, the capture zone is computed dynamically based on leg type, ground speed, etc.

This is a prerequisite for #9761.

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References

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Testing instructions

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