[SPARK-30599][CORE][TESTS] Increase the maximum number of log events in LogAppender

### What changes were proposed in this pull request?
Increased the limit for log events that could be stored in `SparkFunSuite.LogAppender` from 100 to 1000.

### Why are the changes needed?
Sometimes (see traces in SPARK-30599) additional info is logged via log4j, and appended to `LogAppender`. For example, unusual log entries are:
```
[36] Removed broadcast_214_piece0 on 192.168.1.66:52354 in memory (size: 5.7 KiB, free: 2003.8 MiB)
[37] Removed broadcast_204_piece0 on 192.168.1.66:52354 in memory (size: 5.7 KiB, free: 2003.9 MiB)
[38] Removed broadcast_200_piece0 on 192.168.1.66:52354 in memory (size: 3.7 KiB, free: 2003.9 MiB)
[39] Removed broadcast_207_piece0 on 192.168.1.66:52354 in memory (size: 24.2 KiB, free: 2003.9 MiB)
[40] Removed broadcast_208_piece0 on 192.168.1.66:52354 in memory (size: 24.2 KiB, free: 2003.9 MiB)
```
and a test which uses `LogAppender` can fail with the exception:
```
java.lang.IllegalStateException: Number of events reached the limit of 100 while logging CSV header matches to schema w/ enforceSchema.
```

### Does this PR introduce any user-facing change?
No

### How was this patch tested?
By re-running `"SPARK-23786: warning should be printed if CSV header doesn't conform to schema"` in a loop.

Closes #27312 from MaxGekk/log-appender-filter.

Authored-by: Maxim Gekk <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: MaxGekk

core/src/test/scala/org/apache/spark/SparkFunSuite.scala

@@ -189,7 +189,7 @@ abstract class SparkFunSuite
     }
   }
 
-  class LogAppender(msg: String = "", maxEvents: Int = 100) extends AppenderSkeleton {
+  class LogAppender(msg: String = "", maxEvents: Int = 1000) extends AppenderSkeleton {
     val loggingEvents = new ArrayBuffer[LoggingEvent]()
 
     override def append(loggingEvent: LoggingEvent): Unit = {