feat: inject OTTL statements from elasticapm connector to lsmintervaltree processor

[inge4pres]

Reason for this PR

Some data manipulations that are necessary in the elasticapm connector can be achieved with OTTL transforms, especially now that an upstream feature in OTTL to read from context is merged and released
open-telemetry/opentelemetry-collector-contrib#41879

Details

• Create a new field Statements that is part of the elasticapm connector config to allow forwarding OTTL statements to downstream components
• append the statements to existing ones
• propagate execution to lsmintervaltree processor

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 8618ff13-4961-4d0a-896d-9b7e70d10457

📥 Commits

Reviewing files that changed from the base of the PR and between 2759cf4 and 965d2a9.

📒 Files selected for processing (3)

• connector/elasticapmconnector/config.go
• connector/elasticapmconnector/connector_test.go
• processor/lsmintervalprocessor/processor.go

✅ Files skipped from review due to trivial changes (1)

• processor/lsmintervalprocessor/processor.go

🚧 Files skipped from review as they are similar to previous changes (2)

• connector/elasticapmconnector/connector_test.go
• connector/elasticapmconnector/config.go

---

📝 Walkthrough

Walkthrough

This change extends the Elastic APM connector to support injecting custom OTTL statements into per-interval metric processing. The AggregationConfig struct gains a Statements field to specify additional rules. The processor's metadata handling was refactored to create per-iteration contexts, enabling OTTL statements to access otelcol.client.metadata during execution. A new test validates that OTTL statements can conditionally rewrite metric attributes based on client metadata values.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch elasticapmconnector/custom-statements

• 🛠️ Update Documentation: Commit on current branch
• 🛠️ Update Documentation: Create PR

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}