Clean up typescript types related to rust crypto (#4706)

* Simplify bootstrapSecretStorage logic

might as well just export the keys immediately, rather than having multiple
tests.

* Clean up typescript types related to rust crypto

A forthcoming release of matrix-rust-sdk-crypto-wasm tightens up a number of
typescript types. In preparation, we need to get our house in order too.

spec/unit/rust-crypto/rust-crypto.spec.ts

@@ -213,7 +213,7 @@ describe("initRustCrypto", () => {
             jest.spyOn(Migration, "migrateMegolmSessions").mockResolvedValue(undefined);
 
             const testOlmMachine = makeTestOlmMachine();
-            testOlmMachine.trackedUsers.mockResolvedValue([]);
+            testOlmMachine.trackedUsers.mockResolvedValue(new Set([]));
             jest.spyOn(OlmMachine, "initFromStore").mockResolvedValue(testOlmMachine);
         });
 
@@ -806,11 +806,6 @@ describe("RustCrypto", () => {
                     asJSON: jest.fn().mockReturnValue("{}"),
                 }),
                 saveBackupDecryptionKey: jest.fn(),
-                crossSigningStatus: jest.fn().mockResolvedValue({
-                    hasMaster: true,
-                    hasSelfSigning: true,
-                    hasUserSigning: true,
-                }),
                 exportCrossSigningKeys: jest.fn().mockResolvedValue({
                     masterKey: "sosecret",
                     userSigningKey: "secrets",