Remove dependency on cb lib

[kmannislands]

Description

Remove dependency on 10 year old cb library. The downside of the supply chain security vector of this lib (especially when used in sensitive middle ware like this) outweighs the trivial utility that express-oidc-connect was getting from the dependency. It was being used only to memoize callbacks in 3 locations.

References

Closes #423

Testing

All unit tests passing should cover this change as it is very straight-forward. Code inspection of the cb lib indicated that this should behave identically.

Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not the default branch

[adamjmcgrath]

Thanks @kmannislands