br restore failed with "Unknown character set: 'gbk'" if table CHARSET=gbk

[fubinzh]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. Create tidb cluster with below parameters:

new_collations_enabled_on_first_bootstrap = true
[experimental]
enable-new-charset = true

2. Create table with charset gbk

create database gbktest; 
use gbktest;
create table gbk1(a int primary key, b varchar(20) charset gbk) collate gbk_bin; 
insert into gbk1 value (1, "GBK测试");

3. Use br to backup the db

./br backup db --pd "172.16.6.217:2379" --db gbktest --storage "local:///home/tools_test_data/gbktest_backup"

4. Use br to restore the db

2. What did you expect to see? (Required)

Restore table whose charset = gbk should succeed.

3. What did you see instead (Required)

Restore failed

[root@centos76_vm v5.4.0]#  ./br restore db --pd "172.16.6.217:2379" --db gbktest --storage "local:///home/tools_test_data/gbktest_backup"
Detail BR log in /tmp/br.log.2022-01-04T18.47.15+0800
Database restore <---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------> 100.00%
[2022/01/04 18:47:15.801 +08:00] [INFO] [collector.go:67] ["Database restore failed summary"] [total-ranges=0] [ranges-succeed=0] [ranges-failed=0] [split-region=3.309264ms] [restore-ranges=1]
Error: [ddl:1115]Unknown character set: 'gbk'

4. What is your TiDB version? (Required)

[root@centos76_vm v5.4.0]# ./br -V
Release Version: v5.4.0
Git Commit Hash: 974b578
Git Branch: heads/refs/tags/v5.4.0
Go Version: go1.16.4
UTC Build Time: 2022-01-04 07:43:43
Race Enabled: false

[3pointer]

fixed in #31291

[github-actions]

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