Support MySQL 8.4

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The current version of Percona Toolkit is incompatible with the latest LTS release of MySQL 8.4. Among other things, the new MySQL version removed the deprecated SHOW SLAVE HOSTS statement (should be SHOW REPLICAS).

See https://perconadev.atlassian.net/browse/PT-2340

As soon es the next Percona Toolkit Version is released, we can

• update PT Toolkit:

  liquibase-percona/pom.xml

  Line 49 in d059fca

  <percona.toolkit.version>3.5.7</percona.toolkit.version>

• update default MySQL for integration tests to 8.4:

  liquibase-percona/pom.xml

  Line 64 in d059fca

  <mysql_image>mysql:8.2</mysql_image>

• Update GitHub Actions to run against MySQL 8.0.x and 8.4.x:

  liquibase-percona/.github/workflows/test.yml

  Line 33 in d059fca

  mysql: ["8.0", "8.2"]