test: load the popup's libraries once per test file, not on every boot (closes #428)

Every popup boot in the tests resets jest's module registry so that src/
loads fresh, and that also reloaded ethers, libsodium-wrappers-sumo, qrcode
and ethereum-blockies-base64 each time: more than half of a boot, and
tests/persistedFieldContract.test.js boots the popup 321 times.
tests/support/popupBoot.js now loads those four once per test file and hands
the same copies to every boot. No test or assertion changed. make test takes
10-15s on the shared build host instead of 23-29s.

Model: opus-5-5

tests/support/popupBoot.js

@@ -20,6 +20,17 @@ const path = require("path");
 
 const { makeStorageStub } = require("./storageStub");
 
+// The four libraries the popup loads from node_modules, loaded once per test
+// file and handed to every boot. jest.resetModules() in bootPopup() would
+// otherwise load them again on every boot, which was more than half of what a
+// boot cost. None of them holds popup state; everything under src/ is still
+// loaded fresh on each boot. A test that mocks one of these itself has its mock
+// replaced by bootPopup().
+const ethers = require("ethers");
+const sodium = require("libsodium-wrappers-sumo");
+const QRCode = require("qrcode");
+const makeBlockie = require("ethereum-blockies-base64");
+
 const POPUP_HTML = fs.readFileSync(
     path.join(__dirname, "..", "..", "src", "popup", "index.html"),
     "utf8",
@@ -219,6 +230,11 @@ async function settle() {
 async function bootPopup(stored, options) {
     jest.resetModules();
 
+    jest.doMock("ethers", () => ethers);
+    jest.doMock("libsodium-wrappers-sumo", () => sodium);
+    jest.doMock("qrcode", () => QRCode);
+    jest.doMock("ethereum-blockies-base64", () => makeBlockie);
+
     // The three modules that reach the network. None is on the path under
     // test; all would make the suite hit the internet.
     jest.doMock("../../src/shared/prices", () => ({