test: apply fast retries to the proof-attach RLN registration

test_rln_proof_attach.nim (added in #4069) postdates this branch, so its
node-internal register() — on the manager created during RLN mount — still
paid the 4s production retry delay on every receipt poll. Apply
withFastRetries() to it, matching the other node-internal managers this
branch already speeds up.

Also reflows setupOnchainGroupManager's sendMintCall to nph after the
Opt.some conversion made during the rebase conflict resolution (master
migrated Option -> Opt while this branch was open).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/messaging/test_rln_proof_attach.nim

@@ -75,9 +75,9 @@ suite "SendService RLN proof attach - RLN mounted":
 
     let credentials = generateCredentials()
     (
-      waitFor cast[OnchainGroupManager](waku.node.rln.groupManager).register(
-        credentials, UserMessageLimit(20)
-      )
+      waitFor cast[OnchainGroupManager](waku.node.rln.groupManager)
+        .withFastRetries()
+        .register(credentials, UserMessageLimit(20))
     ).isOkOr:
       assert false, "failed to register RLN credentials: " & error
 

tests/waku_rln_relay/utils_onchain.nim

@@ -746,7 +746,12 @@ proc setupOnchainGroupManager*(
     return
 
   await sendMintCall(
-    web3, web3.defaultAccount, testTokenAddress, acc, ethToWei(1000.u256), Opt.some(0.u256)
+    web3,
+    web3.defaultAccount,
+    testTokenAddress,
+    acc,
+    ethToWei(1000.u256),
+    Opt.some(0.u256),
   )
 
   let contractAddress = (await executeForgeContractDeployScripts(privateKey, acc, web3)).valueOr: