ElementR: Add `CryptoApi.getCrossSigningStatus` (#3452)
* Add `crypto.getCrossSigningStatus`
* Fix imports and boolean casting
* Moved `isStoredInSecretStorage` into a single function
* Review changes `CrossSigningStatus`
* Review changes for `cross-signing.spec.ts`
* Add test in case when cross signing is not setup
* Handle when the `crossSigningStatus` returned by the olmMachine is null
* Review changes for `crypto-api` documentation
* Update `cross-signing.spec.ts` according to review changes
* Moved and renamed `isStoredInSecretStorage`
* Remove noise in `CrossSigning.ts` imports
* Fix `returns` sentence in `secretStorageContainsCrossSigningKeys`
* Fix typos
* Add test for `secret-storage.ts`
* Improve documentation
* Add doc about fetch mock request name
