[V2 experimentation]profiler: remove WithAPIKey and WithAgentlessUpload

[JianyiGao]

What does this PR do?

Remove WithAPIKey option
#866

Motivation

TLDR:
Agentless uploading is originally supported if customer set DD_API_KEY env variable, or use WithAPIKey option. WithAgentlessUpload was introduced for debugging purpose when agentless mode is disabled for WithAPIKey option.

Due to business reasons we want to deprecate agentless support for public uses, only allow internal usage by explicitly set DD_PROFILING_AGENTLESS and DD_API_KEY env variable.

This PR is to remove WithAPIKey and WithAgentlessUpload option.

More context: Agentless vs Agent Uploading

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.

For Datadog employees:

• If this PR touches code that handles credentials of any kind, such as Datadog API keys, I've requested a review from @DataDog/security-design-and-guidance.
• This PR doesn't touch any of that.

Unsure? Have a question? Request a review!

[pr-commenter]

Benchmarks

Benchmark execution time: 2023-09-22 13:43:25

Comparing candidate commit 0a7f739 in PR branch jennie.gao/remove-withapikey with baseline commit 2ac90e1 in branch jennie.gao/v2-experimentation-main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 39 metrics, 2 unstable metrics.

[felixge]

This is a breaking API change. Please ping me in slack to provide more context on this. Thanks!

cc @nsrip-dd

Edit: Talked to Jennie about this in slack. This is for v2 and not going into the main branch.

[felixge]

LGTM