Fix the sync point SanitizeOptions::AfterChangeMaxOpenFiles which is not executed in db_compaction_test (#11583)

Summary:
In [db_impl_open.cc](https://github.com/facebook/rocksdb/blob/main/db/db_impl/db_impl_open.cc), the sync point `SanitizeOptions::AfterChangeMaxOpenFiles` is used to set `max_open_files` with some specified "**invalid**" value even if it has been sanitized.

However,  in [db_compaction_test.cc](https://github.com/facebook/rocksdb/blob/main/db/db_compaction_test.cc), `SanitizeOptions::AfterChangeMaxOpenFiles` would not be executed since `SyncPoint::EnableProcessing()` is run after `DBTestBase::Reopen()`.  To enable `SanitizeOptions::AfterChangeMaxOpenFiles`,  `SyncPoint::EnableProcessing()` should be put ahead of `DBTestBase::Reopen()`.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/11583

Test Plan:
run unit tests locally as below:
```
make J=1 check

[ RUN      ] DBCompactionTest.LevelTtlCascadingCompactions
[       OK ] DBCompactionTest.LevelTtlCascadingCompactions (85 ms)
[ RUN      ] DBCompactionTest.LevelPeriodicCompaction
[       OK ] DBCompactionTest.LevelPeriodicCompaction (57 ms)
```

Reviewed By: jowlyzhang

Differential Revision: D47311827

Pulled By: ajkr

fbshipit-source-id: 99165e87a8129e404af06fdf9b4c96eca540fd23

db/db_compaction_test.cc

@@ -4600,6 +4600,7 @@ TEST_F(DBCompactionTest, LevelTtlCascadingCompactions) {
               PutVarint64(encoded_fieled, 0);
             }
           });
+      ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
 
       options.env = env_;
 
@@ -4616,7 +4617,6 @@ TEST_F(DBCompactionTest, LevelTtlCascadingCompactions) {
               ttl_compactions++;
             }
           });
-      ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
 
       // Add two L6 files with key ranges: [1 .. 100], [101 .. 200].
       Random rnd(301);
@@ -4748,6 +4748,7 @@ TEST_F(DBCompactionTest, LevelPeriodicCompaction) {
               PutVarint64(encoded_fieled, 0);
             }
           });
+      ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
 
       options.env = env_;
 
@@ -4764,7 +4765,6 @@ TEST_F(DBCompactionTest, LevelPeriodicCompaction) {
               periodic_compactions++;
             }
           });
-      ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
 
       Random rnd(301);
       for (int i = 0; i < kNumLevelFiles; ++i) {