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. tests/support/popupBoot.js now loads
those four once per test file and registers them once with jest.doMock(),
which jest.resetModules() keeps, so every boot gets the same copies. No test
or assertion changed. make test takes 8-13s on the shared build host, down
from 17-25s, measured in alternating runs before and after the change.

Model: opus-5-5

script/test

@@ -5,12 +5,12 @@
 # many-core shared host one per core took gigabytes of RAM per run.
 #
 # The timeout bounds a hung suite; it is not a performance budget. On the busy
-# shared build host the suite takes 23-29s with three workers, so
-# REPO_POLICIES' 30s cap is tight there, not comfortable. Inside the image the
-# same suite also pays a cold jest cache and shares the runner with the rest of
-# the build, which is not what that budget describes, so the Dockerfile raises
-# the bound through AUTISTMASK_TEST_TIMEOUT. A cap a healthy suite can trip on a
-# cold cache produces a red that means nothing, and teaches "just run it again".
+# shared build host the suite takes 8-13s with three workers, inside
+# REPO_POLICIES' 20s budget. Inside the image the same suite also pays a cold
+# jest cache and shares the runner with the rest of the build, which is not what
+# that budget describes, so the Dockerfile raises the bound through
+# AUTISTMASK_TEST_TIMEOUT. A cap a healthy suite can trip on a cold cache
+# produces a red that means nothing, and teaches "just run it again".
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"