ci: fix node-versions run for node <16 (#1653)

* re-add updating to npm v7 for node versions <16
* only upgrade npm for node v <16
* fix bin/rlp js: node 12 doesn't support ES11 which added support for nullish coalescing operator (??) so we'll use ternary here
alternatively we could write this file in TS and compile to e.g. dist/bin/rlp (like we do in the client bin), but maybe if the file gets more complicated, in its current state i don't think it's so neccessary
* use same errorMsg format for JSON.parse, remove unneeded extra Uint8Array.from (already is uint8array)

.github/workflows/node-versions.yml

@@ -40,6 +40,10 @@ jobs:
           node-version: ${{ matrix.node }}
           cache: 'npm'
 
+      - name: Use npm v7 for workspaces support
+        run: npm i -g npm@7
+        if: ${{ matrix.node-version < 16 }}
+
       - run: npm i
 
       - name: Test Block

packages/rlp/bin/rlp

@@ -16,15 +16,17 @@ if (method === 'encode') {
   try {
     json = JSON.parse(strInput)
   } catch (error) {
-    return console.error(`Error could not parse JSON: ${JSON.stringify(error)}`)
+    const errorMsg = error.message ? error.message : error
+    return console.error(`Error could not parse JSON: ${errorMsg}`)
   }
 
   // Encode RLP
   try {
     const encoded = RLP.encode(json)
-    console.log('0x' + bytesToHex(Uint8Array.from(encoded)))
+    console.log('0x' + bytesToHex(encoded))
   } catch (error) {
-    console.error(`Error encoding RLP: ${error.message ?? error}`)
+    const errorMsg = error.message ? error.message : error
+    console.error(`Error encoding RLP: ${errorMsg}`)
   }
 } else if (method === 'decode') {
   // Decode
@@ -33,7 +35,8 @@ if (method === 'encode') {
     const json = JSON.stringify(arrToJSON(decoded))
     console.log(json)
   } catch (error) {
-    console.error(`Error decoding RLP: ${error.message ?? error}`)
+    const errorMsg = error.message ? error.message : error
+    console.error(`Error decoding RLP: ${errorMsg}`)
   }
 } else {
   console.error('Unsupported method')