chore(papi): keep the upstream sources in upstream-src/

The pezkuwi-dev build treats any package with a src/ directory as its
own: it requires our license header on every file and builds it. These
are upstream files that must stay byte-identical to the source embedded
in dist/, so they live in upstream-src/ instead, which neither the build
nor the root tsconfig picks up.

packages/papi-utils/upstream-src/jsonPrint.ts

@@ -0,0 +1,11 @@
+export const jsonPrint = (value: any, indent = 2) =>
+  JSON.stringify(
+    value,
+    (_, v) =>
+      typeof v === "bigint"
+        ? `${v}n`
+        : typeof v === "object" && typeof v?.asHex === "function"
+          ? v.asHex()
+          : v,
+    indent,
+  )