Stick to mysql 8.3 for the time being

MySQL 8.4 does not load the 'mysql_native_password' plugin by default
and I couldn't figure out how to initialise the container to load it.

Run one testsuite with observers enabled in CI (#13869)

Signed-off-by: Bob Weinand <bobwei9@hotmail.com>

CircleCI: Increase no_output_timeout to 30m

Move ARM build to CircleCI

Closes GH-12415