COMPLETES SPARK-509669

This pull request addresses

2 device registrations occur in the Calling SDK.

calling.register which calls the internal.device.register from webex/calling.js
line.register which does the Mobius line registration

While we have the above two methods for deregistering, we do not have a deregister method only for line and not for calling which does the WDM device deletion operation

by making the following changes

This PR introduces that method in webex/calling.js - The Calling class such that, users can do this deregister upon successful deregistering of line
Or, they can call calling.deregister() method alone which will deregister all the active lines, disconnect mercury and delete WDM device as well

Recording

In the below recordings, you can see that the WDM device and Mercury registration doesn't happen before this change and they happen in the after-change screen recording,

Before:

https://github.com/webex/webex-js-sdk/assets/8044050/e7d7bb7a-c03f-4eac-8256-637a4f123419

After:

calling.deregister cleans up active lines automatically and deletes the WDM registration

https://github.com/webex/webex-js-sdk/assets/8044050/b0af4d86-cac5-4a56-b9ae-6d6e84b8437b

calling.deregister just deletes the WDM registration

https://github.com/webex/webex-js-sdk/assets/8044050/2eb4af9f-e965-42b8-a7c6-5a0889e25da1

Change Type

[x] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)
[ ] Documentation update
[ ] Tooling change
[ ] Internal code refactor

The following scenarios where tested

Tested if the device registers and deregisters
Tried registering and deregistering several times to see if the "User has excessive device registrations" error pops up and it doesn't now

I certified that

[x] I have read and followed contributing guidelines
[x] I discussed changes with code owners prior to submitting this pull request
[x] I have not skipped any automated checks
[x] All existing and new tests passed
[x] I have updated the documentation accordingly

Make sure to have followed the contributing guidelines before submitting.

webex / webex-js-sdk

fix(calling): wdm deregister method #3609