Add support for subentries to config entries (#117355)
* Add support for subentries to config entries
* Improve error handling and test coverage
* Include subentry_id in subentry containers
* Auto-generate subentry_id and add optional unique_id
* Tweak
* Update tests
* Fix stale docstring
* Address review comments
* Typing tweaks
* Add methods to ConfigEntries to add and remove subentry
* Improve ConfigSubentryData typed dict
* Update test snapshots
* Adjust tests
* Fix unique_id logic
* Allow multiple subentries with None unique_id
* Add number of subentries to config entry JSON representation
* Add subentry translation support
* Allow integrations to implement multiple subentry flows
* Update translations schema
* Adjust exception text
* Change subentry flow init step to user
* Prevent creating a subentry with colliding unique_id
* Update tests
* Address review comments
* Remove duplicaetd unique_id collision check
* Remove change from the future
* Improve test coverage
* Add default value for unique_id
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