Decouple initial refreshes in setup for Environment Canada

[gwww]

Proposed change

When the integration is being setup and if one of the coordinators is down (most often see radar not available) then the entire integration is unavailable, instead of just the one coordinator (of the three) that is down.

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

There are two "parts" to this PR. The first bit is decoupling the DataUpdateCoordinator initial refreshes. The second bit is to fix all the places in the entities that break because the initial refresh of the data failed. Most of those are pretty straight forward. The only one I want to highlight is that the unique_id for sensor is initialized from a different data source -- the unique_ids have not changed.

Big thank you to @thecode who helped me understand the options for how this is fixed.

We considered two approaches for this change. The approach that can be seen in the first commit in this PR was discarded as entities would show with unknown values when their corresponding DataUpdateCoordinator fails. The approach taken in the final PR show entities as Unavailable when their corresponding DataUpdateCoordinator fails.

• This PR fixes or closes issue: fixes #Environment Canada fails to start: cannot identify image file #64849
• This PR is related to issue:
• Link to documentation pull request:

Checklist

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[probot-home-assistant]

Hey there @michaeldavie, mind taking a look at this pull request as it has been labeled with an integration (environment_canada) you are listed as a code owner for? Thanks!
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