Use Uint32 for SEQ_IN_INDEX in 'SHOW INDEXES' queries.

[mkrautz]

This is seemingly the correct type for this field.

MySQL Connector/NET expects this for servers >8.0.1: https://github.com/mysql/mysql-connector-net/blob/8.4.0/MySQL.Data/src/SchemaProvider.cs#L298-L300

Fixes #2501

[timsehn]

@jycor is going to review.

[jycor]

Thanks @mkrautz for the contribution!
This looks great.

Happy to merge this after adding this one test:

diff --git a/enginetest/queries/information_schema_queries.go b/enginetest/queries/information_schema_queries.go
index 7524dad0e..f31032f5e 100644
--- a/enginetest/queries/information_schema_queries.go
+++ b/enginetest/queries/information_schema_queries.go
@@ -335,6 +335,23 @@ var InfoSchemaQueries = []QueryTest{
        },
        {
                Query: `SHOW INDEXES FROM mytaBLE`,
+               ExpectedColumns: sql.Schema{
+                       &sql.Column{Name: "Table", Type: types.LongText},
+                       &sql.Column{Name: "Non_unique", Type: types.Int32},
+                       &sql.Column{Name: "Key_name", Type: types.LongText},
+                       &sql.Column{Name: "Seq_in_index", Type: types.Uint32},
+                       &sql.Column{Name: "Column_name", Type: types.LongText, Nullable: true},
+                       &sql.Column{Name: "Collation", Type: types.LongText, Nullable: true},
+                       &sql.Column{Name: "Cardinality", Type: types.Int64},
+                       &sql.Column{Name: "Sub_part", Type: types.Int64, Nullable: true},
+                       &sql.Column{Name: "Packed", Type: types.LongText, Nullable: true},
+                       &sql.Column{Name: "Null", Type: types.LongText},
+                       &sql.Column{Name: "Index_type", Type: types.LongText},
+                       &sql.Column{Name: "Comment", Type: types.LongText},
+                       &sql.Column{Name: "Index_comment", Type: types.LongText},
+                       &sql.Column{Name: "Visible", Type: types.LongText},
+                       &sql.Column{Name: "Expression", Type: types.LongText, Nullable: true},
+               },
                Expected: []sql.Row{
                        {"mytable", 0, "PRIMARY", 1, "i", nil, 0, nil, nil, "", "BTREE", "", "", "YES", nil},
                        {"mytable", 0, "mytable_s", 1, "s", nil, 0, nil, nil, "", "BTREE", "", "", "YES", nil},

[mkrautz]

Thanks! I was about to add the test myself, since I didn't get to it yesterday. :-)