* Document and support the established naming convention for config opts
This change:
* Rename `ConfigOptions` to `IConfigOptions` to match code convention/style, plus move it to a dedicated file
* Update comments and surrounding documentation
* Define every single documented option (from element-web's config.md)
* Enable a linter to enforce the convention
* Invent a translation layer for a different change to use
* No attempt to fix build errors from doing this (at this stage)
* Add demo of lint rule in action
* Fix all obvious instances of SdkConfig case conflicts
* Fix tests to use SdkConfig directly
* Add docs to make unset() calling safer
* Appease the linter
* Update documentation to match snake_case_config
* Fix more instances of square brackets off SdkConfig
* Add matrix-analytics-events as a dependency
* Make IEvent look like a stub definition
* Update pageview tracking to track screens, using a hypothetical definition of a screen event
* Remove distinction between pseudo and anon tracking, will need to rework it considering stubs
* Add a new flag pseudonymousAnalyticsOptIn replacing analyticsOptIn, stored at account level, so people only need to opt in once.
* Show a toast in login to users that have analyticsOptIn set but not yet pseudonymousAnalyticsOptIn prompting them confirm the new method is okay. Update the copy of the existing opt-in toast. Don't notify users that previously opted out.
* Update the copy in settings
* Add a new learn more dialog
* Support a new config flag analyticsOwner which is used in these toasts when explaining which entity the data is sent to ("Help improve %(analyticsOwner)"). If unset, display brand. This allows deployments whose brand differs from the receiver of the analytics to explain the situation to their users (e.g. AcmeCorp badges their app, but explains the data is sent to Element, not them)
* The new opt-in and flags are only used when posthog is configured; prior to that there are no changes to UX or tracking behaviour.
IEvent.properties is a placeholder that needs to be overriden by extenders for type validation to take place.
IWelcomeScreenLoad should have had properties declared for it. Because it didn't, a faulty call using it was possible.
