opentelemetry: allow empty strings for TraceID and SpanID (logs) [Backport to 4.0]

[cosmo0920]

Backporting of #10956.

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Testing
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• Example configuration file for the change
• Debug log output from testing the change

• Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• Run local packaging test showing all targets (including any new ones) build.
• Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• Documentation required for this feature

Backporting

• Backport to latest stable release.

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✨ Finishing touches

🧪 Generate unit tests

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch in_opentelemetry_empty_trace_span-4.0

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[niedbalski]

🔄 Backported to FluentDo Agent

This change has been backported to FluentDo Agent.

• FluentDo PR: feat: sync upstream Fluent Bit from v4.0.11 to upstream/4.0 telemetryforge/agent#18
• FluentDo PR Title: feat: sync upstream Fluent Bit from v4.0.11 to upstream/4.0
• Upstream Commit: d06b62f

You can view the test results and integration status in the FluentDo Agent PR.

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This is an automated notification from FluentDo Agent's backport tracking system.