Rework Shelly sensors

[balloob]

Breaking change

Proposed change

Reworks Shelly sensors to:

• use an attribute descriptor class with helper entity
• sensors are now tied to block type + attribute name instead of just attribute name
• Use same infra for binary sensors
• Add sensor index to name if multiple blocks with same type

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• 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

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• This PR fixes or closes issue: fixes #
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[probot-home-assistant]

Hey there @bieniu, mind taking a look at this pull request as its been labeled with an integration (shelly) you are listed as a codeowner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[MartinHjelmare]

Looks good!

[bieniu]

@balloob Was that the intention to remove some sensors? For example, the power sensor for some devices is in relay block, for some in device for others in emeter.

[balloob]

Those need to be added back but felt out of scope for this PR. For now I just picked one of the types that had them. Used data from the new verify script for this home-assistant-libs/aioshelly#11

[bieniu]

I understand, I was not sure if this is an intended change. In the evening I will add the missing sensors.