[opt](cache) enhance cache key computation by removing comments and t…

…rimming SQL input (#46099)

- Currently, the SQL cache system in Doris may miss cache hits due to
semantically identical queries being treated as different because of:
  - Extra whitespace characters in the SQL query
  - SQL comments that don't affect the query execution
- For example, these queries are semantically identical but would
generate different cache keys:
  ```sql
  SELECT * FROM table;
  -- Same query with comments and extra spaces
  /* Comment */  SELECT   *   FROM   table  ;
  ```
- This PR improves the SQL cache hit rate by:
  - Trimming whitespace from SQL queries
  - Removing SQL comments before calculating the cache key MD5
- This ensures that queries that are semantically identical but differ
only in whitespace or comments will now hit the same cache entry,
improving cache efficiency and reducing unnecessary query executions

fe/fe-core/src/main/java/org/apache/doris/nereids/SqlCacheContext.java

@@ -26,6 +26,7 @@
 import org.apache.doris.mysql.FieldInfo;
 import org.apache.doris.mysql.privilege.DataMaskPolicy;
 import org.apache.doris.mysql.privilege.RowFilterPolicy;
+import org.apache.doris.nereids.parser.NereidsParser;
 import org.apache.doris.nereids.trees.expressions.Expression;
 import org.apache.doris.nereids.trees.expressions.Variable;
 import org.apache.doris.nereids.util.Utils;
@@ -349,7 +350,7 @@ public PUniqueId getOrComputeCacheKeyMd5() {
 
     /** doComputeCacheKeyMd5 */
     public synchronized PUniqueId doComputeCacheKeyMd5(Set<Variable> usedVariables) {
-        StringBuilder cacheKey = new StringBuilder(originSql);
+        StringBuilder cacheKey = new StringBuilder(NereidsParser.removeCommentAndTrimBlank(originSql.trim()));
         for (Entry<FullTableName, String> entry : usedViews.entrySet()) {
             cacheKey.append("|")
                     .append(entry.getKey())