fix(eval/latencies): generate metadata for warmup_rate

This removes the requirement where we had to put `warmup_rate` value in
the list of rates that we test. This speeds up the test and also allows
us to test only one variant, when there is only one rate value.

evaluation/scripts/collect-latencies.mts

@@ -39,9 +39,9 @@ const bookinfo_variants = new Set([
 ] as const)
 /**
  * Which variants to test during this run.
- * Note, that there has to be more than one variant here, since with one
- * variant, there is some weird behavior where each second attack fails for
- * most of the requests.
+ * Note, that there has to be more than one variant here if we are testing more
+ * than one rate value. That is because with one variant, there is some weird
+ * behavior where each second attack fails for most of the requests.
  */
 const test_only = new Set<VARIANT>([
   "plain",
@@ -86,7 +86,7 @@ await (async function main() {
   )
 
   const metadata_map = new Map<RATE, Map<VARIANT, METADATA>>()
-  for (const rate of rates) {
+  for (const rate of new Set<RATE>([warmup_rate, ...rates])) {
     const map = new Map<VARIANT, METADATA>()
 
     for (const variant of test_only) {