[Enhancement] Allow Legal Hold Custodian user list generation

[natrlhy]

Summary

Included a new option/switch to list all the custodians in a legal hold matter

Proposed API

Create new option called users
legal-hold list users -m, --matter-id <matter_id>

Intended Use Case

This would allow one to pull a list of users/custodians in a specific matter. Very useful on very large legal holds. Paul Hirsts C42LegalHoldReportsMac script is failing/timing out just due to the large number of legal hold users