consider using defensive traits where appropriate

[enthusiastmartin]

Consider using defensive traits

https://github.com/paritytech/substrate/blob/master/frame/support/src/traits/misc.rs

where it would be appropriate and helpful.

Mostly places where you expect infallible code ( basically places where comments such as "cannot happen" , "should not happen", "it is safe because of previous condition" are found,)

Eg.

• defensive_ok_or
• defensive_saturating_add
• etc.

This would be helpful in following way:

1. it panics on debug_assertion, which means if you reach this error in tests, it panics.
2. it logs error in production using runtime logging system. Which might help detecting potential problems.