Fix to work with apiml customized token name

[1000TurquoisePogs]

Proposed changes

This PR changes sso-auth to identify the correct name of the APIML cookie when it is customized. Prior, sso-auth could only handle the default cookie name.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

PR Checklist

Please delete options that are not relevant.

• If the changes in this PR are meant for the next release / mainline, this PR targets the "staging" branch.
• My code follows the style guidelines of this project (see: Contributing guideline)
• I have made corresponding changes to the documentation
• New and existing unit tests pass locally with my changes
• Relevant update to CHANGELOG.md
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works, or describe a test method below

Testing

Setup APIML customized cookie as described within https://672897b8df9db03907cd59a6--zowe-docs-master.netlify.app/stable/user-guide/api-mediation/configuration-unique-cookie-name-for-multiple-zowe-instances

Then, check to see if you can login to the desktop.
Do not check if the editor works. This requires a change in ZSS which will be in a separate PR. It is expected not to work until then.