If localStorage is not available, use a in-memory none expiring assig…

[leoromanovsky]

…nment cache (FF-2110)

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labels: mergeable

Fixes: #issue

Motivation and Context

When init is called, a localStorage assignment cache is created. However if no localStorage is available it always returns non-cachable return values, effectively being no cache. This is going to happen on chrome extensions and other environments without a localStorage.

Description

• If no localStorage is available, create an in-memory assignment cache. This is an improvement over the current behavior as at least there will be some caching happening, even though it is reset each session.
• extracted helper methods in environment.ts
• moved assignment cache files into own directory

How has this been tested?

[leoromanovsky]

IMO no need for these methods - the class should only be instantiated from the factory and when localStorage is detected. If not, throwing an exception is "good" behavior so the end-user uses the more appropriate class.