[integ-tests-framework] Use Lazy import of dependencies in reports_generator

[hanwen-cluster]

Description of changes

Sometimes, only a few functions in reports_generator.py are called by a environment, which doesn't have to have all Python dependencies installed

Tests

• test will run after the PR is merge

Checklist

• Make sure you are pointing to the right branch.
• If you're creating a patch for a branch other than develop add the branch name as prefix in the PR title (e.g. [release-3.6]).
• Check all commits' messages are clear, describing what and why vs how.
• Make sure to have added unit tests or integration tests to cover the new/modified code.
• Check if documentation is impacted by this change.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (integ-tests-3.15.0@b6b4e59). Learn more about missing BASE report.

Additional details and impacted files

@@                  Coverage Diff                  @@
##             integ-tests-3.15.0    #7313   +/-   ##
=====================================================
  Coverage                      ?   90.08%           
=====================================================
  Files                         ?      182           
  Lines                         ?    16730           
  Branches                      ?        0           
=====================================================
  Hits                          ?    15071           
  Misses                        ?     1659           
  Partials                      ?        0           

Flag	Coverage Δ
unittests	90.08% <ø> (?)

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[gmarciani]

This is a short term solution to prevent alarms.
The long term solution is to remove the dependency on SUPPORTED_OS constant and install pandas and other dependencies in Jenkins.