Clean up local workflow

[swiatekm]

Clean up and reorganize make targets used most frequently during local development. The intent is to make the new contributor experience better and to avoid unnecessary dependencies between the targets.

The actual changes are as follows:

• make test no longer runs anything other than tests. Previously it also ran fmt, vet and generate.
• make manager no longer does anything other than building the manager binary. Previously it depended on some other unnecessary targets.
• make precommit is a new target that includes all the local checks, excluding e2e tests.
• Updated CONTRIBUTING.md to reflect the changes and removed some outdated info.

[pavolloffay]

generate generates deepcopy methods for the api package wich seems fundamental for manager binary

[swiatekm]

I don't think there's any reason to run it every time we build the manager, though. We don't do this for other binaries.

I'm generally of the opinion that targets like generate shouldn't be too implicit. I'm not sure whether including it as a dependency everywhere isn't more confusing to a new contributor vs having to run it manually when they make changes to api types.

[pavolloffay]

The majority of contributors don't know what the generate command does. There is not even documentation that for the change on the objects in the api package the command should be run.

[swiatekm]

This is actually documented here: https://github.com/open-telemetry/opentelemetry-operator/blob/main/CONTRIBUTING.md#make-changes-to-the-project-manifests.

But in general, I think this is ok. If the contributor should've run generate, but didn't, the CI will catch that, as will running make precommit.

What I'm trying to achieve with this PR is to not surprise users with changes to files in version control. Running tests or building the operator binary should not do this, in my view, even if it may be convenient at times.

[pavolloffay]

I will not argue anymore but it mentions manifests not the API package.

[pavolloffay]

I am fine splitting manifest generation from the compilation. But I would expect that compilation produces up-to-date binaries.

[swiatekm]

I can see that argument. In that case, should I also add generate to the opamp bridge make target?

[swiatekm]

For the record, I definitely disagree with running fmt as part of this target, so I guess me and operator-sdk are enemies now. 🗡️

[pavolloffay]

I think we should be consistent and if opapm requires the generate command it should be added as well.

[swiatekm]

Added generate as a dependency of both manager and opamp-bridge.