Add support for JSON fragments

[bdraco]

Proposed change

#102870 (comment)

Currently we have multiple copies a state in memory in different formats depending on which api asks for them. This will allow for better reuse of objects between formats and reduce the amount of serializations.

A common case for this is serializing state_changed Event objects since new_state and old_state can now use the previously serialized fragment instead of recreating it again. Additionally restore state can now reuse the fragment instead of serializing again each time it writes to disk.

We also avoid constructing a lot of ReadOnlyDict for the cases were the data is never exposed outside of core and only used to create json.

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• Dependency upgrade
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• Breaking change (fix/feature causing existing functionality to break)
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• This PR fixes or closes issue: fixes #
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[home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as it has been labeled with an integration (websocket_api) you are listed as a code owner for? Thanks!

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[bdraco]

Thanks