Docker setup for localtests

[meiji163]

Description

This PR adds a docker container setup for running the replica tests in localtest/, since it can be hard to get dbdeployer working locally, and it is no longer maintained. Eventually we can use docker for the replica tests in CI as well.
Tested with mysql:8.0.39 on darwin arm64 and linux amd64.

Usage:

docker-gh-ost-replica-tests up # bring containers up
docker-gh-ost-replica-tests run # run localtests
docker-gh-ost-replica-tests down # remove containers
TEST_MYSQL_IMAGE="mysql:8.0.16" docker-gh-ost-replica-tests up # change the mysql image

In case this PR introduced Go code changes:

• contributed code is using same conventions as original code
• script/cibuild returns with no formatting errors, build errors or unit test errors.

Copilot reviewed 2 out of 6 changed files in this pull request and generated no comments.

Files not reviewed (4)

• localtests/test.sh: Language not supported
• script/docker-gh-ost-replica-tests: Language not supported
• script/gh-ost-test-mysql-master: Language not supported
• script/gh-ost-test-mysql-replica: Language not supported

Comments suppressed due to low confidence (3)

localtests/docker-compose.yml:3

• The environment variable TEST_MYSQL_IMAGE is not defined within the docker-compose file. Ensure that this variable is set in the environment where the docker-compose command is run.

image: $TEST_MYSQL_IMAGE

localtests/docker-compose.yml:11

• The MySQL container is configured to use port 3307, which is non-standard and may conflict with other services. Ensure this port is available or consider using the default MySQL port 3306.

- '3307:3307'

localtests/docker-compose.yml:23

• The MySQL replica container is configured to use port 3308, which is non-standard and may conflict with other services. Ensure this port is available or consider using the default MySQL port 3306.

- '3308:3308'

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