can't use collate clause for json when the new collation is enabled

[wjhuang2016]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

CREATE TABLE `tt` (
  `a` char(10) COLLATE utf8mb4_general_ci DEFAULT NULL,
  `b` enum('a','B','c') COLLATE utf8mb4_general_ci DEFAULT NULL,
  `c` set('a','B','c') COLLATE utf8mb4_general_ci DEFAULT NULL,
  `d` json DEFAULT NULL
)
select min(d collate utf8mb4_bin) from tt;

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

No error

3. What did you see instead (Required)

Error 1253: COLLATION 'utf8mb4_bin' is not valid for CHARACTER SET 'binary'

4. What is your TiDB version? (Required)

master

[yudongusa]

@wjhuang2016 since SQL team has been working collation related refactor and improvement, assign the collation related issues to sig/sql-infra for now.