Add support for device dehydration v2

[uhoreg]

Rehydrates/dehydrates device if dehydration is enabled in .well-known file (or if there is a dehydration key in SSSS). (Currently, js-sdk only supports dehydration when using Rust crypto.)

Dehydrated devices are hidden or displayed specially when they are cross-signed, and if there is only one. Otherwise, they are displayed as normal devices.

Checklist

• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• Sign-off given on the changes (see CONTRIBUTING.md).

[uhoreg]

Looks like SonarCloud doesn't consider the playwright tests? Because some of the lines that it's complaining about not being tested are tested in playwright.

[t3chguy]

Looks like SonarCloud doesn't consider the playwright tests?

Correct, because even just launching the app would hit like 30% overall test coverage without any useful assertions

[richvdh]

Suggested change

	* Dehydration can only be enabled if encryption is available, and the crypto
	* backend supports dehydration.
	* Note that this doesn't necessarily mean that device dehydration has been initialised
	* (yet) on this client; rather, it means that the server supports it, the crypto backend
	* supports it, and the application configuration suggests that it *should* be
	* initialised on this device.

[richvdh]

Ok. I suggest you make an issue about it if you don't expect to have it done in very short order.

[richvdh]

As @t3chguy implies: I'm afraid you'll need to write jest tests to get the coverage up. Hopefully it should be pretty easy.

[uhoreg]

Yup, I'll try to write some stuff to make SonarCloud happy

[richvdh]

@uhoreg Did you get a chance to make an issue?

[richvdh]

LGTM. The tests look very comprehensive!