fix(ci): retry forge solc fetch on transient DNS failures

[AztecBot]

Problem

PR #24352 (and others) intermittently fail in the merge queue with a DNS error. The failing step is the barretenberg/sol test command:

Command: ...cd barretenberg/sol && forge test --no-match-contract Base
Error: error sending request for url (https://binaries.soliditylang.org/linux-amd64/list.json)
Context:
- Error #0: client error (Connect)
- Error #1: dns error
- Error #2: failed to lookup address information: Temporary failure in name resolution

forge reaches out to binaries.soliditylang.org to resolve/fetch the solc binary. Under heavy parallel merge-queue load the VPC resolver intermittently drops lookups (Temporary failure in name resolution), and the operation fails with no retry, taking the whole CI run down with it.

Fix

Retry the solc-fetching forge operations every 10s for ~5 min (30 attempts), scoped to connection/DNS failures so genuine errors still fail fast.

• ci3/retry: make the attempt count tunable via RETRY_ATTEMPTS (default unchanged at 3); RETRY_SLEEP was already honored (default 5s). Fully backward-compatible — existing callers are unaffected.
• barretenberg/sol/bootstrap.sh: wrap the forge test test command in RETRY_ATTEMPTS=30 RETRY_SLEEP=10 retry -p '<dns/connect regex>'. This is the operation that fails in the merge queue.
• l1-contracts/bootstrap.sh: the root svm download (the "single owner of the svm download") already had a short retry; extend it to the same 10s/5-min window and scope it to DNS/connection errors. (2>/dev/null removed so retry's pattern matcher can see the DNS error on stderr.)

The -p pattern (dns error|Temporary failure in name resolution|error sending request|failed to lookup address|Connection refused|connection reset) means a real forge test assertion failure or compile error is not retried — it exits immediately, so this never masks real failures or wastes 5 minutes on a genuinely broken test.

Verification

Exercised ci3/retry and the exact emitted barretenberg/sol command locally:

• DNS-matching failure → retries up to RETRY_ATTEMPTS, sleeping RETRY_SLEEP between attempts.
• Real test failure (no DNS text) → fails fast, no retry (0s).
• Success → returns 0 on the first attempt (0s).
• RETRY_ATTEMPTS unset → still 3 attempts (backward-compatible).

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Created by claudebox · group: slackbot

[AztecBot]

✅ Successfully backported to backport-to-v5-next-staging #24360.