feat(datadog): expose agents.containers.otelAgent.syncDelay to configure otel-agent startup sync timeout

[gb8may]

What this PR does / why we need it:

What

Adds agents.containers.otelAgent.syncDelay (default: 30s) to control
how long otel-agent waits for the core agent to be ready on startup,
replacing the previously hardcoded --sync-delay=30s flag on both Linux
and Windows.

Why

datadog/agent:7.81.1 (shipped with chart >=3.234.0) initializes slower
than previous versions. On fresh node starts with otelCollector.enabled: true,
otel-agent times out waiting for the core agent and enters CrashLoopBackOff
before the core agent is ready to accept connections.

The --sync-delay flag already exists in the binary but was not exposed as a
chart value, leaving users no way to increase it without a post-render patch.

How to use

agents:
  containers:
    otelAgent:
      syncDelay: 60s  # increase from default 30s for agent >= 7.81.1

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #

Special notes for your reviewer:

• Default remains 30s — fully backwards compatible
• Applies to both Linux and Windows target systems
• Verified fix on Kubernetes / AWS EKS with chart 3.235.0

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• All commits are signed and show as "Verified" on GitHub (see: signing commits)
• Chart Version semver bump label has been added (use <chartName>/minor-version, <chartName>/patch-version, or <chartName>/no-version-bump)
• For datadog or datadog-operator chart or value changes, update the test baselines (run: make update-test-baselines)
• For datadog chart changes, received ✅ from a member of your team

GitHub CI takes care of the below, but are still required:

• Documentation has been updated with helm-docs (run: .github/helm-docs.sh)
• CHANGELOG.md has been updated
• Variables are documented in the README.md

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