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

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 10-15s 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)"