Fix webostv YAML migration failure if the entity is removed

[thecode]

Proposed change

Fix webostv YAML migration failure if the entity is removed before the TV is online.
At startup we check if there are entities to be migrated and wait for a connection with the device. Since this process can be very long, the user can delete the entities or do a new paring with the TV, this PR adds a check again before we do the actual unique id update to make sure the entity is still available.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes Migration from configuration.yaml WebOSTV fails when loading the new integration version #64174
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.
• Untested files have been added to .coveragerc.

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To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[probot-home-assistant]

Hey there @bendavid, mind taking a look at this pull request as it has been labeled with an integration (webostv) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[MartinHjelmare]

Looks good!