wtclient: Activate watchtower client by default and also add a Deactivate flag

[priyanshiiit]

Change Description

Fixes: #5344

At present, the --wtclient.active has to be passed to enable the watchtower client but with this PR wtclient is automatically created, however, if not needed it could be disabled using --wtclient.deactivate flag.

[lightninglabs-deploy]

@priyanshiiit, remember to re-request review from reviewers when ready

[lightninglabs-deploy]

@priyanshiiit, remember to re-request review from reviewers when ready

[ellemouton]

Something to note here is that if the wtclient is turned on by default without also adding a tower server, then this will cause a memory leak as backups will be queued in memory until a tower is registered. See https://github.com/lightningnetwork/lnd/issues/5983 and https://github.com/lightningnetwork/lnd/discussions/7286

This will be less of a problem when a fix for https://github.com/lightningnetwork/lnd/issues/5983 (a queue that overflows to disk) is implemented. But also we should probably warn the user that they need to add a tower for this flag to be of any use

[lightninglabs-deploy]

@priyanshiiit, remember to re-request review from reviewers when ready

[ellemouton]

!lightninglabs-deploy mute

[ellemouton]

Hi @priyanshiiit - I have muted this for now since it seems in-active and also given my previous comment. Feel free to unmute the bot once you are ready to hop back on