Race condition when using go-cmp on structs that include `time.Time`

[dhiaayachi]

👋

This a follow-up to golang/go#74460 in the golang issues tracker, where go present a data race when some of the private fields of time.Time are accessed trough the reflect package.

The Golang team decided not to fix the issue as it have implication on the maintainability of private fields in the standard library and suggested to fix go-cmp to treat time.Time as a special case and use == to compare time fields as that's the way go recommend comparing time.Time (read comments on golang/go#74460 for more details).