make adaptive rate limit configurable

Author: kwannoel

e2e_test/backfill/adaptive-rate-limit/amplification-100.slt

@@ -10,7 +10,7 @@ statement ok
 insert into fact select 1 from generate_series(1, 250000);
 
 statement ok
-insert into dim select 1 from generate_series(1, 100);
+insert into dim select 1 from generate_series(1, 1000);
 
 statement ok
 flush;

src/stream/src/executor/backfill/arrangement_backfill.rs

@@ -111,8 +111,7 @@ where
         let upstream_table_id = self.upstream_table.table_id();
         let mut upstream_table = self.upstream_table;
         let vnodes = upstream_table.vnodes().clone();
-        let rate_limit = self.rate_limit;
-        self.chunk_size = 1;
+        let mut rate_limit = self.rate_limit;
 
         // These builders will build data chunks.
         // We must supply them with the full datatypes which correspond to
@@ -149,7 +148,9 @@ where
         };
         tracing::debug!(target: "adaptive_rate_limit", highest_barrier_latency, threshold_barrier_latency, "initial configs");
         let adaptive_rate_limit = true;
-        let mut rate_limit = Some(INITIAL_ADAPTIVE_RATE_LIMIT);
+        if adaptive_rate_limit {
+            rate_limit = Some(INITIAL_ADAPTIVE_RATE_LIMIT);
+        }
 
         // Poll the upstream to get the first barrier.
         let first_barrier = expect_first_barrier(&mut upstream).await?;
@@ -557,7 +558,7 @@ where
 
                 // Adapt Rate Limit
                 if adaptive_rate_limit {
-                    Self::adapt_rate_limit_3(
+                    Self::adapt_rate_limit_2(
                         &self.actor_id,
                         &self.metrics,
                         threshold_barrier_latency,