[testbed] Add resource limits to benchmark results file

[bacherfl]

Component(s)

testbed

Is your feature request related to a problem? Please describe.

Currently, the benchmark results file generated by the testbed includes the achieved max and average values for the CPU and memory usage - see here. It would however also be useful to include the CPU/memory limits specified for the respective test as well, to be able to visualise how close the actual consumption is to the limits.
Therefore I'd like to propose adding these values to the generated overview

Describe the solution you'd like

Modify the PerformanceResults.Add() method to also include the limits for the CPU and memory consumption.

Describe alternatives you've considered

No response

Additional context

I'm already on a PR for this, will post it here soon

[github-actions]

Pinging code owners:

• testbed: @open-telemetry/collector-approvers

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