Group Member utility script include for retrieving and managing group memberships

[AnandMahajan2799]

PR Description:

Created a utility script include for managing user-group relationships.

It provides methods to:
Retrieve users in a group (getGroupMembers)
Retrieve groups a user belongs to (getUserGroups)
Add users to a group (addGroupMembers)
Remove users from a group (removeGroupMembers)

Supports both client and server-side operations.
Ideal for use in server scripts, GlideAjax calls, reference qualifiers, etc to streamline group membership management.

Pull Request Checklist

Overview

• I have read and understood the CONTRIBUTING.md guidelines
• My pull request has a descriptive title that accurately reflects the changes
• I've included only files relevant to the changes described in the PR title and description
• I've created a new branch in my forked repository for this contribution

Code Quality

• My code is relevant to ServiceNow developers
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Repository Structure Compliance

• I've placed my code snippet(s) in one of the required top-level categories:
  • Core ServiceNow APIs/
  • Server-Side Components/
  • Client-Side Components/
  • Modern Development/
  • Integration/
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• I've used appropriate sub-categories within the top-level categories
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• My PR does not include XML exports of ServiceNow records
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• My PR does not include changes that fall outside the described scope

[am-shakeel]

Thank you for your contribution. However, it doesn’t comply with our contributing guidelines. As a reminder, the general requirements (as outlined in the CONTRIBUTING.md file) are the following: follow the folder+subfolder+snippetfolder guidelines and include a readme.md file explaining what the code snippet does. Review your contribution against the guidelines and make the necessary adjustments.

@AnandMahajan2799 - As this is your 1st ever pull request. Please update the PR Title to proceed further

[am-shakeel]

🎉 Congratulations on your first approved PR!
Thank you for your persistence and for finally aligning with the contribution guidelines. Your effort is appreciated—keep up the great work and continue contributing to the community!