Move threads e2e tests over to cypress (#8501)

* Add non-consent (default) Synapse template

* Add consent test

* Add create room test

* Stash work

* Initial threads tests

* fix

* Delete old threads e2e tests, plan new ones

* Fix typed s'more

* Try something else

* specify d.ts

* Fix types once and for all?

* Fix the consent tests

* Iterate threads test harness

* Fix dispatcher types

* Iterate threads test

* fix typing

* Alternative import attempt

* let it break let it break let it break

* Tweak types

* Stash

* delint and update docs

* null-guard scrollIntoView

* Iterate threads test

* Apply suggestions from code review

cypress/support/synapse.ts

@@ -60,7 +60,8 @@ function startSynapse(template: string): Chainable<SynapseInstance> {
     return cy.task<SynapseInstance>("synapseStart", template);
 }
 
-function stopSynapse(synapse: SynapseInstance): Chainable<AUTWindow> {
+function stopSynapse(synapse?: SynapseInstance): Chainable<AUTWindow> {
+    if (!synapse) return;
     // Navigate away from app to stop the background network requests which will race with Synapse shutting down
     return cy.window().then((win) => {
         win.location.href = 'about:blank';