Replace the pyjwkest dependency

[dralley]

Version
All

Describe the bug
pyjwkest has been unmaintained for 4 years, we need to replace it with a library that is maintained.

Additional context
Possibly PyJWT?

[lubosmj]

This is related to #1509. After removing the conversion machinery, we will eliminate code paths that use the pyjwkest dependency.

[lubosmj]

I am closing this since it appears that it is plausible to package pyjwkest with pinned dependencies that do not exhibit vulnerabilities for older releases. For the new releases, we are removing it completely, as mentioned in the comment above.