Add agentless and standalone OpenFeature smoke tests

[PerfectSlayer]

What Does This Do

Extracts the shared OpenFeature smoke test scenarios into AbstractOpenFeatureSmokeTest and runs them in three setups: SDK only (standalone), SDK + agent in agentless mode, and SDK + agent with Remote Configuration. Updates ARCHITECTURE.md.

Motivation

Covers each supported setup of the standalone SDK (APMLP-1512).

Stack

The full change is in #12709. It was split into this stack to ease the review.

1. Resolve Feature Flags enablement from instrumenter config #12845
2. Add dd-openfeature SDK flag configuration and evaluation core #12840
3. Add dd-openfeature SDK settings and configuration delivery #12841
4. Add dd-openfeature SDK exposure and flag evaluation pipelines #12842
5. Add dd-openfeature SDK OpenFeature provider #12843
6. Connect the dd-openfeature SDK to the agent #12844
7. Add agentless and standalone OpenFeature smoke tests #12846 👈 this PR

Jira ticket: APMLP-1512

🤖 Generated with Claude Code

[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	13.97 s	14.05 s	[-1.2%; -0.0%] (maybe better)
startup:insecure-bank:tracing:Agent	12.98 s	13.07 s	[-1.3%; -0.1%] (maybe better)
startup:petclinic:appsec:Agent	17.13 s	16.99 s	[-0.3%; +1.9%] (no difference)
startup:petclinic:iast:Agent	16.98 s	17.06 s	[-1.1%; +0.3%] (no difference)
startup:petclinic:profiling:Agent	16.57 s	16.95 s	[-3.2%; -1.2%] (significantly better)
startup:petclinic:sca:Agent	17.04 s	16.82 s	[+0.4%; +2.2%] (maybe worse)
startup:petclinic:tracing:Agent	16.26 s	16.05 s	[+0.1%; +2.6%] (maybe worse)

Commit: 4db3136f · CI Pipeline · Benchmarking Platform UI

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Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.