[SPARK-29542][SQL][DOC] Make the descriptions of spark.sql.files.* be clearly

### What changes were proposed in this pull request?
As described  in [SPARK-29542](https://issues.apache.org/jira/browse/SPARK-29542) , the descriptions of `spark.sql.files.*` are confused.
In this PR, I make their descriptions be clearly.

### Why are the changes needed?
It makes the descriptions of `spark.sql.files.*` be clearly.
### Does this PR introduce any user-facing change?
No.

### How was this patch tested?
Existing UT.

Closes #26200 from turboFei/SPARK-29542-partition-maxSize.

Authored-by: turbofei <fwang12@ebay.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>

Author: turboFei

sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala

@@ -980,7 +980,9 @@ object SQLConf {
       .createWithDefault(true)
 
   val FILES_MAX_PARTITION_BYTES = buildConf("spark.sql.files.maxPartitionBytes")
-    .doc("The maximum number of bytes to pack into a single partition when reading files.")
+    .doc("The maximum number of bytes to pack into a single partition when reading files. " +
+      "This configuration is effective only when using file-based sources such as Parquet, JSON " +
+      "and ORC.")
     .bytesConf(ByteUnit.BYTE)
     .createWithDefault(128 * 1024 * 1024) // parquet.block.size
 
@@ -989,19 +991,24 @@ object SQLConf {
     .doc("The estimated cost to open a file, measured by the number of bytes could be scanned in" +
       " the same time. This is used when putting multiple files into a partition. It's better to" +
       " over estimated, then the partitions with small files will be faster than partitions with" +
-      " bigger files (which is scheduled first).")
+      " bigger files (which is scheduled first). This configuration is effective only when using" +
+      " file-based sources such as Parquet, JSON and ORC.")
     .longConf
     .createWithDefault(4 * 1024 * 1024)
 
   val IGNORE_CORRUPT_FILES = buildConf("spark.sql.files.ignoreCorruptFiles")
     .doc("Whether to ignore corrupt files. If true, the Spark jobs will continue to run when " +
-      "encountering corrupted files and the contents that have been read will still be returned.")
+      "encountering corrupted files and the contents that have been read will still be returned. " +
+      "This configuration is effective only when using file-based sources such as Parquet, JSON " +
+      "and ORC.")
     .booleanConf
     .createWithDefault(false)
 
   val IGNORE_MISSING_FILES = buildConf("spark.sql.files.ignoreMissingFiles")
     .doc("Whether to ignore missing files. If true, the Spark jobs will continue to run when " +
-      "encountering missing files and the contents that have been read will still be returned.")
+      "encountering missing files and the contents that have been read will still be returned. " +
+      "This configuration is effective only when using file-based sources such as Parquet, JSON " +
+      "and ORC.")
     .booleanConf
     .createWithDefault(false)