gmake run-broker, gmake start-cluster: use a very short plugin list by default

[michaelklishin]

Currently both commands start a node with all plugins. That's never the user's intent and it can result in confusing plugin conflicts that would never have happened in any real world plugin configuration.

Breaking Changes

These changes only affect RabbitMQ developers and contributors.

Now to list a number of plugins, they (us) must use another make variable, ENABLED_PLUGINS:

# enables rabbitmq_management
gmake start-cluster NODES=3

# enables rabbitmq_management
gmake run-broker

# enables multiple plugins
gmake start-cluster NODES=3 ENABLED_PLUGINS="rabbitmq_management rabbitmq_federation rabbitmq_federation_management rabbitmq_shovel rabbitmq_shovel_management rabbitmq_stream rabbitmq_stream_management"

# enables multiple plugins
gmake run-broker ENABLED_PLUGINS="rabbitmq_management rabbitmq_federation rabbitmq_federation_management rabbitmq_shovel rabbitmq_shovel_management rabbitmq_stream rabbitmq_stream_management"

This had to be done because PLUGINS defines both the enabled plugins at runtime and
a list of dependencies, which we do not mean to modify.

Per discussion with @lhoguin @deadtrickster @mkuratczyk.

[michaelklishin]

@lukebakken @the-mikedavis @SimonUnge FYI, since this affects every contributor, I must bring this proposed change to your attention.

[deadtrickster]

lgtm

[gomoripeti]

thank you for this change, I haven't had issues yet with conflicting plugins but often have to disable the trust store plugin to not spam the logs.
I assume this does not affect community plugin workflow. IIRC when I run make run-broker for a community plugin it already did not enable all the plugins, only that particular plugin.

[Zerpet]

I agree to this change. I never had the need to have all plugins enabled 🙂 This PR has cli test failures, which I haven't seen before. I don't think this plugin is the cause, I just wanted to highlight the test failure.

[michaelklishin]

@gomoripeti if you gmake run-broker from a specific plugin directory, only that plugin and its dependencies are enabled. That does not change.

[lukebakken]

I'm so used to always having PLUGINS=rabbitmq_management rabbitmq_top in my shell history I never even considered having the default change. Thanks!

[the-mikedavis]

I agree, using just a small subset is a better default 👍

[michaelklishin]

I don't think this plugin is the cause, I just wanted to highlight the test failure.

FTR, @Zerpet was right. The change was legit because our standard CLI tools' test suites depend on a specific plugin set being configured, and it relied on the PLUGINS gmake variable for that.

I have addressed that failure before merging.