Add a check in write_ops_exec::performUpdate() to reject updates on cold collections.

This single interception point blocks all update operations identified in the decision doc:

• `update`,
• `updateOne`,
• `updateMany`,
• `replaceOne`,
• `findAndModify` (update mode),
• `findOneAndUpdate`,
• `findOneAndReplace`,
• `bulkWrite` (update ops),
• `$merge`

 Pseudo code in performUpdate() (write_ops_exec.cpp):

if (!remove && collection.exists() && collection.getCollectionPtr()->getRecordStore()->isColdCollection()) {
    uasserted(ErrorCodes::IllegalOperation,
    str::stream() << "Updates are not supported on cold collection '"
                  << collection.nss().toStringForErrorMsg() << "'");
} 

Verify `findAndModify` with `remove: true` is NOT blocked (the `remove` parameter in `performUpdate()` distinguishes this case – the cold check should only apply when `!remove`).