Support prefix index

[GaoYusong]

{
		Name: "Prefix index with same columns as another index",
		SetUpScript: []string{
			"CREATE table t (pk int primary key, col1 varchar(100));",
			"INSERT into t values (1, '100'), (2, '200');",
			"alter table t add unique index idx1 (col1);",
		},
		Assertions: []ScriptTestAssertion{
			{
				Query:    "alter table t add index idx2 (col1(10));",
				Expected: []sql.Row{{types.NewOkResult(0)}},
			},
			{
				Query: "show create table t",
				Expected: []sql.Row{{"t",
					"CREATE TABLE `t` (\n" +
						"  `pk` int NOT NULL,\n" +
						"  `col1` varchar(100),\n" +
						"  PRIMARY KEY (`pk`),\n" +
						"  UNIQUE KEY `idx1` (`col1`),\n" +
						"  KEY `idx2` (`col1`(10))\n" +
						") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin"}},
			},
		},
	}

--- FAIL: TestAlterTable (4.95s)
    --- FAIL: TestAlterTable/Prefix_index_with_same_columns_as_another_index (0.03s)
        --- FAIL: TestAlterTable/Prefix_index_with_same_columns_as_another_index/show_create_table_t (0.01s)
            /Users/shannon/code/myduckserver/evaluation.go:726: 
                	Error Trace:	/Users/shannon/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.2-0.20240815142344-761713e36043/enginetest/evaluation.go:726
                	            				/Users/shannon/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.2-0.20240815142344-761713e36043/enginetest/evaluation.go:357
                	Error:      	Not equal: 
                	            	expected: []sql.Row{sql.Row{"t", "CREATE TABLE `t` (\n  `pk` int NOT NULL,\n  `col1` varchar(100),\n  PRIMARY KEY (`pk`),\n  UNIQUE KEY `idx1` (`col1`),\n  KEY `idx2` (`col1`(10))\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin"}}
                	            	actual  : []sql.Row{sql.Row{"t", "CREATE TABLE `t` (\n  `pk` int NOT NULL,\n  `col1` varchar(100),\n  PRIMARY KEY (`pk`),\n  UNIQUE KEY `idx1` (`col1`),\n  KEY `idx2` (`col1`)\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin"}}
                	            	
                	            	Diff:
                	            	--- Expected
                	            	+++ Actual
                	            	@@ -3,3 +3,3 @@
                	            	   (string) (len=1) "t",
                	            	-  (string) (len=205) "CREATE TABLE `t` (\n  `pk` int NOT NULL,\n  `col1` varchar(100),\n  PRIMARY KEY (`pk`),\n  UNIQUE KEY `idx1` (`col1`),\n  KEY `idx2` (`col1`(10))\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin"
                	            	+  (string) (len=201) "CREATE TABLE `t` (\n  `pk` int NOT NULL,\n  `col1` varchar(100),\n  PRIMARY KEY (`pk`),\n  UNIQUE KEY `idx1` (`col1`),\n  KEY `idx2` (`col1`)\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin"
                	            	  }
                	Test:       	TestAlterTable/Prefix_index_with_same_columns_as_another_index/show_create_table_t
                	Messages:   	Unexpected result for query show create