perf(hash-join): gate union-bounds fast path on pushdown_filters=false

Previously the union-bounds fast path fired whenever
enable_hash_join_dynamic_membership_filter=false (the production
default). But that also relaxes the filter for pushdown_filters=true,
where arrow-rs RowFilter amortizes the per-row CASE hash-routed cost
via lazy decode of the remaining columns for filtered rows — the
tighter per-partition selectivity is worth paying for there.

This commit couples the fast path to the runtime pushdown_filters
setting: the SharedBuildAccumulator now mirrors
execution.parquet.pushdown_filters and picks the shape based on
where the filter will run:

  * pushdown_filters=false → probe scan applies the filter post-decode
    (PostScanFilter, Layer 3). Per-row cost dominates because there is
    no lazy decode to amortize it. Emit the cheap union-of-bounds
    predicate and skip membership entirely.

  * pushdown_filters=true  → probe scan applies the filter via arrow-rs
    RowFilter (Layer 2), which skips the decode of the remaining
    columns for rows that fail the predicate. Emit the historical
    per-partition CASE hash-routed form; respect the user's opt-in via
    enable_hash_join_dynamic_membership_filter for membership.

Effect matrix:

  pushdown_filters | enable_membership_filter | Partitioned filter shape
  -----------------+--------------------------+--------------------------------
  false (default)  | any                      | union bounds (fast path)
  true             | false                    | CASE hash-routed, bounds only
  true             | true                     | CASE hash-routed + membership

Tests:
- New helper make_partitioned_accumulator_pushdown_on_and_membership_{on,off}.
- New unit test partitioned_pushdown_on_membership_off_still_emits_case_no_membership
  — pushdown=true must keep CASE even with membership off.
- New unit test collect_left_pushdown_off_skips_membership_even_with_gate_on
  — pushdown=false must skip membership even with opt-in.
- Existing test fixtures updated to include pushdown_filters explicitly
  (existing coverage kept — bounds-only fixtures set pushdown_filters=false
  to match production default; membership-on fixtures set pushdown_filters=true).

Also refreshes projection_pushdown.slt for an unrelated main-branch
plan-shape change (#23459 CSE tweak) that surfaced post-rebase.

Author: zhuqi-lucas

datafusion/physical-plan/src/joins/hash_join/exec.rs

@@ -1393,6 +1393,18 @@ impl ExecutionPlan for HashJoinExec {
             .options()
             .optimizer
             .enable_hash_join_dynamic_membership_filter;
+        // Mirror the probe scan's parquet `pushdown_filters` config into the
+        // build coordinator so it can pick the cheap union-of-bounds shape
+        // when the probe scan applies the filter post-decode (Layer 3), and
+        // the historical per-partition CASE hash-routing when the probe
+        // scan applies it via arrow-rs `RowFilter` with lazy decode
+        // (Layer 2). See #23701.
+        let pushdown_filters = context
+            .session_config()
+            .options()
+            .execution
+            .parquet
+            .pushdown_filters;
         let build_accumulator = enable_dynamic_filter_pushdown
             .then(|| {
                 self.dynamic_filter.as_ref().map(|df| {
@@ -1412,6 +1424,7 @@ impl ExecutionPlan for HashJoinExec {
                             repartition_random_state,
                             self.null_aware,
                             enable_membership_filter,
+                            pushdown_filters,
                         ))
                     })))
                 })