Create _ghc table failed When Rocksdb enable rocksdb_strict_collation_check

```
show global variables like 'rocksdb_strict_collation_%';
+-------------------------------------+-------+
| Variable_name | Value |
+-------------------------------------+-------+
| rocksdb_strict_collation_check | ON |
| rocksdb_strict_collation_exceptions | |
+-------------------------------------+-------+

```

Error 12009 (HY000): Unsupported collation on string indexed column {db_name}._xxx_ghc.hint Use binary collation (binary, latin1_bin, utf8_bin).

Start by reproducing the failure with rocksdb_strict_collation_check enabled, using the shown SHOW GLOBAL VARIABLES query and the _ghc table creation path. Trace how gh-ost creates the table and identify why the string-indexed column uses an unsupported collation. Done means the _ghc table is created successfully with the setting enabled.

Written by the indexing model from the issue text.