Update to use the new TokenCache interface

[EngHabu]

TL;DR

Update flytectl pkce token cache to implement the new interface methods

Type

• [X] Bug Fix
• [ ] Feature
• [ ] Plugin

Are all requirements met?

• [X] Code completed
• [X] Smoke tested
• [X] Unit tests added
• [X] Code documentation added
• [X] Any pending items have an associated Issue

Tracking Issue

https://github.com/flyteorg/flyte/issues/