Add user email notification preferences feature (merge feature branch into version branch)

[ryaplots]

Summary

References #7308

This PR is a merger of BE and FE parts of the feature.

• https://github.com/TheThingsNetwork/lorawan-stack/pull/7363
• https://github.com/TheThingsNetwork/lorawan-stack/pull/7349

Testing

Steps

1. log in as admin into the console
2. select a notification types you want to receive email for
3. Then trigger sending some notifications. If the email notification type is selected the user should receive an email for that, if it is unselected the user should not receive an email.

Notes for Reviewers

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Checklist

• [x] Scope: The referenced issue is addressed, there are no unrelated changes.
• [x] Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• [ ] Documentation: Relevant documentation is added or updated.
• [x] Testing: The steps/process to test this feature are clearly explained including testing for regressions.
• [ ] Infrastructure: If infrastructural changes (e.g., new RPC, configuration) are needed, a separate issue is created in the infrastructural repositories.
• [x] Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• [x] Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.