[SDK-2833] Fix issue where errors were being cached

[adamjmcgrath]

Description

Using the sync lru-memoizer was caching the promise per kid, rather than the result of the promise per kid. So if the first request failed, the rejected promise would stay in the cache and be reused for subsequent requests.

Have switched to the async lru-memoizer which caches the result of the async function, so if the async function fails the result will not be cached. This required a callback type signature funciton and returned a callback signature function. So the input promise function needed to be callbackified, and the output callback function needed to be promisified.

References

fixes #257

Testing

• This change adds test coverage for new/changed/fixed functionality

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 master