*: Show edition information when mysql client login (#17170)

[sre-bot]

cherry-pick #17170 to release-4.0

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Signed-off-by: Lonng heng@lonng.org

What problem does this PR solve?

Show edition information when MySQL client login and tidb-server -V

Problem Summary:

TiDB needs to distinguish Enterprise and Community editions after v4.0.0 GA, and print the edition information when user login via MySQL client.

What is changed and how it works?

1. Change the Makefile to change the edition according to environment variables.
2. Change the version_comment session variable.

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.7.25-TiDB-v4.0.0 TiDB Server (Apache License 2.0) Enterprise Edition, MySQL 5.7 compatible

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

Tests

• Unit test
• No code

Release note

• No need

[sre-bot]

/run-all-tests

[zhangjinpeng87]

LGTM

[lonng]

/run-common-test