feat: Remove index table existence check (#27509)

Summary:

Remove index table existence check

## Release Notes

```
== NO RELEASE NOTE ==
```

Differential Revision: D99565855

Author: skyelves

presto-main-base/src/main/java/com/facebook/presto/sql/analyzer/StatementAnalyzer.java

@@ -1161,9 +1161,6 @@ protected Scope visitCreateVectorIndex(CreateVectorIndex node, Optional<Scope> s
             }
 
             QualifiedObjectName targetTable = createQualifiedObjectName(session, node, node.getIndexName(), metadata);
-            if (metadataResolver.tableExists(targetTable)) {
-                throw new SemanticException(TABLE_ALREADY_EXISTS, node, "Destination table '%s' already exists", targetTable);
-            }
 
             // Analyze the source table to build a proper scope with typed columns
             // Use AllowAllAccessControl since we check permissions separately below

presto-main-base/src/test/java/com/facebook/presto/sql/analyzer/TestAnalyzer.java

@@ -82,7 +82,6 @@
 import static com.facebook.presto.sql.analyzer.SemanticErrorCode.SAMPLE_PERCENTAGE_OUT_OF_RANGE;
 import static com.facebook.presto.sql.analyzer.SemanticErrorCode.SCHEMA_NOT_SPECIFIED;
 import static com.facebook.presto.sql.analyzer.SemanticErrorCode.STANDALONE_LAMBDA;
-import static com.facebook.presto.sql.analyzer.SemanticErrorCode.TABLE_ALREADY_EXISTS;
 import static com.facebook.presto.sql.analyzer.SemanticErrorCode.TABLE_FUNCTION_COLUMN_NOT_FOUND;
 import static com.facebook.presto.sql.analyzer.SemanticErrorCode.TABLE_FUNCTION_DUPLICATE_RANGE_VARIABLE;
 import static com.facebook.presto.sql.analyzer.SemanticErrorCode.TABLE_FUNCTION_IMPLEMENTATION_ERROR;
@@ -2395,9 +2394,8 @@ public void testCreateVectorIndex()
         assertFails(MISSING_TABLE, ".*Source table '.*' does not exist",
                 "CREATE VECTOR INDEX test_index ON nonexistent_table(a, b)");
 
-        // destination table already exists (using an existing table name as the index name)
-        assertFails(TABLE_ALREADY_EXISTS, ".*already exists",
-                "CREATE VECTOR INDEX t1 ON t2(a, b)");
+        // destination table already exists — allowed (connector decides how to handle)
+        analyze("CREATE VECTOR INDEX t1 ON t2(a, b)");
 
         // column does not exist in source table
         assertFails(MISSING_COLUMN, ".*Column 'unknown' does not exist in source table '.*'",