[Refactor] improve be ut & fix warn compile (StarRocks#39610)

Why I'm doing:

improve two be ut that will cost too much time.
fix compile warn:
[ 99%] Built target Exprs
/root/starrocks/be/src/storage/primary_key_dump.cpp:183:21: warning: private field '_dump' is not used [-Wunused-private-field]
    PrimaryKeyDump* _dump;
                    ^
1 warning generated.

Signed-off-by: luohaha <18810541851@163.com>

be/src/storage/primary_key_dump.cpp

@@ -151,8 +151,7 @@ Status PrimaryKeyDump::_dump_dcg() {
 
 class PrimaryKeyChunkDumper {
 public:
-    PrimaryKeyChunkDumper(PrimaryKeyDump* dump, PrimaryKeyColumnPB* pk_column_pb)
-            : _dump(dump), _pk_column_pb(pk_column_pb) {}
+    PrimaryKeyChunkDumper(PrimaryKeyColumnPB* pk_column_pb) : _pk_column_pb(pk_column_pb) {}
     ~PrimaryKeyChunkDumper() { (void)fs::delete_file(_tmp_file); }
     Status init(const TabletSchemaCSPtr& tablet_schema, const std::string& tablet_path) {
         _tmp_file = tablet_path + "/PrimaryKeyChunkDumper_" + std::to_string(static_cast<int64_t>(pthread_self()));
@@ -180,7 +179,6 @@ class PrimaryKeyChunkDumper {
     }
 
 private:
-    PrimaryKeyDump* _dump;
     PrimaryKeyColumnPB* _pk_column_pb;
     std::unique_ptr<SegmentWriter> _writer;
     PagePointerPB _page;
@@ -258,7 +256,7 @@ Status PrimaryKeyDump::_dump_segment_keys() {
             }
             PrimaryKeyColumnPB pk_column_pb;
             pk_column_pb.set_segment_id(rowset.second->rowset_meta()->get_rowset_seg_id() + i);
-            PrimaryKeyChunkDumper dumper(this, &pk_column_pb);
+            PrimaryKeyChunkDumper dumper(&pk_column_pb);
             RETURN_IF_ERROR(dumper.init(pkey_tschema, _tablet->schema_hash_path()));
             while (true) {
                 chunk->reset();

be/test/storage/persistent_index_test.cpp

@@ -1936,7 +1936,7 @@ TEST_P(PersistentIndexTest, test_bloom_filter_for_pindex) {
 }
 
 TEST_P(PersistentIndexTest, test_multi_l2_tmp_l1) {
-    config::l0_max_mem_usage = 1024;
+    config::l0_max_mem_usage = 50;
     config::max_tmp_l1_num = 10;
     FileSystem* fs = FileSystem::Default();
     const std::string kPersistentIndexDir = "./PersistentIndexTest_test_multi_l2_tmp_l1";
@@ -1946,8 +1946,8 @@ TEST_P(PersistentIndexTest, test_multi_l2_tmp_l1) {
 
     using Key = std::string;
     PersistentIndexMetaPB index_meta;
-    const int N = 1000000;
-    const int wal_n = 200000;
+    const int N = 1000;
+    const int wal_n = 200;
     int64_t cur_version = 0;
     // insert
     vector<Key> keys(N);
@@ -2266,7 +2266,7 @@ TEST_P(PersistentIndexTest, test_multi_l2_not_tmp_l1_fixlen) {
 }
 
 TEST_P(PersistentIndexTest, test_multi_l2_delete) {
-    config::l0_max_mem_usage = 1024;
+    config::l0_max_mem_usage = 50;
     config::max_tmp_l1_num = 10;
     FileSystem* fs = FileSystem::Default();
     const std::string kPersistentIndexDir = "./PersistentIndexTest_test_multi_l2_delete";
@@ -2276,8 +2276,8 @@ TEST_P(PersistentIndexTest, test_multi_l2_delete) {
 
     using Key = std::string;
     PersistentIndexMetaPB index_meta;
-    const int N = 1000000;
-    const int DEL_N = 900000;
+    const int N = 1000;
+    const int DEL_N = 900;
     int64_t cur_version = 0;
     // insert
     vector<Key> keys(N);