Tag pipeline spans with plugin version

[nikita-tkachenko-datadog]

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What does this PR do?

Adds jenkins.plugin.version tag to pipeline spans.
The goal is simplify support, and to allow CI Visibility backend to process pipelines differently based on the plugin version (needed for in-progress pipelines implementation).

Description of the Change

Alternate Designs

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• Feature or bug fix MUST have appropriate tests (unit, integration, etc...)
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