feat(library/standard/data/nat/order): add le_decidable, lt_decidable, ge_decidable, gt_decidable
feat(library/standard/data/nat/order): add le_decidable, lt_decidable, ge_decidable, gt_decidable

Signed-off-by: Leonardo de Moura <7610bae85f2b530654cc716772f1fe653373e892@microsoft.com>

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