Add back configurable access token creation plugin support

[fmeschbe]

Is your feature request related to a problem? Please describe.
IMS access token creation currently only supports JWT based, OAuth2, and CLI access tokens. Other access token types might be added in the future. So it would be beneficial to add back configurable token creation plugin support to add more types of access token creation.

Describe the solution you'd like

• Expose API in the Context class to retrieve and update additional token creation plugins
• Add support to the token generation function to consider the configured token creation plugins in the selection process

Describe alternatives you've considered
n/a

Additional context
n/a

[aiojbot]

JIRA issue created: https://jira.corp.adobe.com/browse/ACNA-1227