feat: support database indexes

[ImpressionableRaccoon]

https://gorm.io/docs/indexes.html
https://ydb.tech/en/docs/yql/reference/syntax/alter_table#secondary-index

behavior now:
db.AutoMigrate() failed when index already created

func TestSequentialAutoMigrateWithIndex(t *testing.T) {
	type Migrations struct {
		ID      string `gorm:"primarykey;not null"`
		Payload string `gorm:"index"`
	}

	dsn, has := os.LookupEnv("YDB_CONNECTION_STRING")
	if !has {
		t.Skip("skip test '" + t.Name() + "' without env 'YDB_CONNECTION_STRING'")
	}

	pathPrefix := t.Name()

	for i := 0; i < 5; i++ {
		t.Run("", func(t *testing.T) {
			db, err := gorm.Open(
				ydb.Open(dsn,
					ydb.WithTablePathPrefix(pathPrefix),
				),
			)
			require.NoError(t, err)
			require.NotNil(t, db)

			db = db.Debug()

			err = db.AutoMigrate(&Migrations{})
			require.NoError(t, err)
		})
	}
}

result:

=== RUN   TestSequentialAutoMigrateWithIndex/#00

[494.824ms] [rows:0] CREATE TABLE `migrations` (`id` Utf8 NOT NULL,`payload` Utf8,PRIMARY KEY (`id`),INDEX `idx_migrations_payload` GLOBAL ON (`payload`))

    --- PASS: TestSequentialAutoMigrateWithIndex/#00 (3.18s)


=== RUN   TestSequentialAutoMigrateWithIndex/#01

[959.834ms] [rows:-] SELECT DATABASE()

[1095.721ms] [rows:-] SELECT count(*) FROM information_schema.statistics WHERE table_schema = $1 AND table_name = $2 AND index_name = $3

[327.297ms] [rows:0] CREATE INDEX `idx_migrations_payload` ON `migrations`(`payload`)

operation/GENERIC_ERROR (code = 400080, address = ..., issues = [{4:0 => 'Unexpected token 'CREATE' : cannot match to any predicted input...'}])
at `github.com/ydb-platform/ydb-go-sdk/v3/internal/conn.(*conn).Invoke(conn.go:361)`
at `github.com/ydb-platform/ydb-go-sdk/v3/internal/balancer.(*Balancer).wrapCall(balancer.go:293)`
at `github.com/ydb-platform/ydb-go-sdk/v3/internal/table.(*session).executeDataQuery(session.go:733)`
at `github.com/ydb-platform/ydb-go-sdk/v3/internal/table.(*session).Execute(session.go:688)`
at `github.com/ydb-platform/ydb-go-sdk/v3/internal/xsql.(*conn).execContext(conn.go:190)`

    --- FAIL: TestSequentialAutoMigrateWithIndex/#01 (5.83s)