Move process discovery out of auto

[MrAlias]

Resolve #1887

• Have the CLI manage process discovery instead of the auto.NewInstrumentation.
  • Parse OTEL_GO_AUTO_TARGET_EXE in the CLI instead of auto.NewInstrumentation
  • Remove the WithTarget option
• Add support for the -target-exe CLI flag to configure the target executable path
• Add support for the -target-pid CLI flag to configure the target pid
• Add support for parsing OTEL_GO_AUTO_TARGET_PID in the CLI
• Add tests for process discovery

[damemi]

@MrAlias wdyt about moving the entire internal/pkg/process to its own top-level package, such as go.opentelemetry.io/auto/process?

This is coming from looking at the Probe api, which is currently tied to the process package through the targetdetails arg

Given that not all probes will be tied to a process, and process detection and management is going to move up to the consumer level, I think it makes sense to not have it be tied in that way. But it could be useful for the consumers who are implementing process management for us to provide that code as a helper package. Curious what you think?

[MrAlias]

@MrAlias wdyt about moving the entire internal/pkg/process to its own top-level package, such as go.opentelemetry.io/auto/process?

This is coming from looking at the Probe api, which is currently tied to the process package through the targetdetails arg

Given that not all probes will be tied to a process, and process detection and management is going to move up to the consumer level, I think it makes sense to not have it be tied in that way. But it could be useful for the consumers who are implementing process management for us to provide that code as a helper package. Curious what you think?

I'm looking at refactoring the process package right now. There is a lot of clean up needed there.

I agree we will need some top-level package to represent a package for the probe API. I'm not in favor of just moving the whole package as is given things I'm seeing there, but we can surely add something at the top level that makes sense when we add the probe API.

That said, I do not plan to move the process package in this PR. I see this as part of the larger refactor of that package and a step towards moving parts of it.

[damemi]

@MrAlias sounds good, and yeah I assumed that there are refactoring changes needed (didn't mean that we could just literally move the entire package wholesale as-is). My main point is having something external that can be used with the external Probe api. I think that will be a prerequisite for that refactor

[MrAlias]

Gotcha, sounds like we're on the same page 😀