Use (time.Time).Equal for time objects

[gfelixc]

Summary

Use built-in Equal method when compare time.Time objects

Changes

When use Equal, try to cast given objects into time.Time and uses (time.Time).Equal in case of true

Motivation

See #1010

Related issues

Closes #1010

Breaking change

[leoleoasd]

Does the exact same thing with #979. #979 is reverted shortly after merge, because, as #984 mentions, this only fixes comparing between time. a struct containing time still cannot be compared. #985 tried to fix this by creating something like reflect.DeepEqual and call time.Time.Equal when needed, but used unsafe pointers.

[brackendawson]

Earlier duplicate of #1464