Bloop generate is automatically called during sbt project loading

[eatkins]

I've noticed with the latest metals that when I start sbt (in the sbt project) I see:

[info] welcome to sbt 1.4.0-M2 (Azul Systems, Inc. Java 1.8.0_252)
[info] loading settings for project sbt-build-build-build from metals.sbt ...
[info] loading project definition from ${SBT_LOCATION}/project/project/project
[info] loading settings for project sbt-build-build from metals.sbt ...
[info] loading project definition from ${SBT_LOCATION}/project/project
[success] Generated .bloop/sbt-build-build.json
[success] Generated .bloop/sbt-build-build.json
[success] Total time: 0 s, completed Aug 20, 2020 11:30:31 AM
[info] loading settings for project sbt-build from local.sbt,metals.sbt,plugins.sbt ...
[info] loading project definition from ${SBT_LOCATION}/project
[success] Generated .bloop/sbt-build.json
[success] Generated .bloop/sbt-build.json
[success] Total time: 1 s, completed Aug 20, 2020 11:30:32 AM

This makes sbt noticeably slower to start up. Without the bloop plugin, I find the sbt project loads in about 9 seconds. With the bloop plugin, it increases to about 11 seconds. I also would prefer not having the success messages displayed during project loading (though they did help make it obvious why startup got slower).

It would be great if the old behavior could be restored where the plugin did not automatically call bloopGenerate on load.

[eatkins]

If reverting to the old behavior is not possible, I have two suggestions that would improve the ux:

1. Log what bloop is doing before calling bloopGenerate. The success messages are mysterious in a vacuum. It is also weird that the same success message is logged twice. It would be better if it looked like:

[info] Generating bloop config for project sbt
[info] Generated .bloop/sbt-build.json
[success] Total time: 1 s, completed Aug 20, 2020 11:30:32 AM

2. Cache the state if possible so that the auto bloop generation happens once the first time the project is loaded and doesn't happen again until something changes. I have no idea if that is possible or how difficult that would be.