fix(op-service): increase Anvil startup timeout from 5s to 30s (ethereum-optimism#19424)

The 5s timeout is too tight under CI load. When 12 parallel test nodes
compete for CPU/IO on a 2xlarge box, Anvil sometimes takes >5s to print
its "Listening on" line, triggering "anvil did not start in time" in
TestImplementations and TestSuperchain. This is the #2 and #3 most
frequent flake in the repo over the last 7 days (67 and 46 incidences).

30s gives Anvil enough headroom on a loaded machine while still failing
fast on a genuine startup failure.

Co-authored-by: smartcontracts <smartcontracts@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: smartcontracts

op-service/testutils/devnet/anvil.go

@@ -114,7 +114,7 @@ func (r *Anvil) Start() error {
 	go r.outputStream(r.stdout)
 	go r.outputStream(r.stderr)
 
-	timeoutC := time.NewTimer(5 * time.Second)
+	timeoutC := time.NewTimer(30 * time.Second)
 
 	select {
 	case <-r.startedCh: