Run jest with --no-sparkplug to avoid V8 GC segfaults on macOS arm64 (#39081)

Run jest with --no-sparkplug to avoid V8 GC segfaults

Sparkplug is V8's baseline JIT. It leaves a stale near-null pointer in an
InternalFrame slot; a later GC conservative stack scan dereferences it and
segfaults. Disabling the tier removes the write, so no crash.

This kills jest workers with SIGSEGV on macOS arm64 CI before any test body
runs, which auto-files an issue against whichever suite happened to be
loading. Eight unrelated suites have been hit since April.

nodejs/node#62393 — fixed in V8 as shipped in Node 25, not backported to the
24 LTS line our mac agents pin. Remove this once agents move off Node 24.

--no-sparkplug can't go in NODE_OPTIONS and .bin/jest is a shell shim that
can't take node flags, hence the explicit bin/jest.js path. Workers inherit
it because jest-worker forks with execArgv.

Author: bbondy

package.json

@@ -37,8 +37,8 @@
     "eslint": "eslint --quiet .",
     "build-storybook": "node ./build/commands/scripts/storybook.ts --command=build",
     "storybook": "node ./build/commands/scripts/storybook.ts --command=dev",
-    "test-unit": "jest",
-    "test-unit:wallet": "jest --coverage=false components/brave_wallet_ui",
+    "test-unit": "node --no-sparkplug node_modules/jest/bin/jest.js",
+    "test-unit:wallet": "node --no-sparkplug node_modules/jest/bin/jest.js --coverage=false components/brave_wallet_ui",
     "update_symlink": "node ./build/commands/scripts/commands.js update_symlink",
     "build_fuzzer": "node ./build/commands/scripts/commands.js build_fuzzer",
     "fuzzer": "node ./build/commands/scripts/commands.js run_fuzzer",