[Backport] Fix Run3 Tracker Geometry Reco config, python3 for geometry package, unit test tracker geo

[srimanob]

PR description:

Backport of #34875, #35092, #35119

[cmsbuild]

A new Pull Request was created by @srimanob (Phat Srimanobhas) for CMSSW_12_0_X.

It involves the following packages:

• Configuration/Geometry (geometry, upgrade)
• Geometry/TrackerGeometryBuilder (geometry)

@civanch, @Dr15Jones, @makortel, @cvuosalo, @ianna, @mdhildreth, @cmsbuild, @AdrianoDee, @srimanob can you please review it and eventually sign? Thanks.
@vargasa, @JanFSchulte, @kpedro88, @VinInn, @Martin-Grunewald, @bsunanda, @mmusich, @mtosi, @fabiocos, @slomeo, @venturia this is something you requested to watch as well.
@perrotta, @dpiparo, @qliphy you are the release manager for this.

cms-bot commands are listed here

[srimanob]

@cmsbuild please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-12b2c0/18310/summary.html
COMMIT: 490d2dc
CMSSW: CMSSW_12_0_X_2021-09-03-2300/slc7_amd64_gcc900
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/35152/18310/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 1457 differences found in the comparisons
• DQMHistoTests: Total files compared: 39
• DQMHistoTests: Total histograms compared: 2998564
• DQMHistoTests: Total failures: 727
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 2997815
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 38 files compared)
• Checked 165 log files, 37 edm output root files, 39 DQM output files
• TriggerResults: found differences in 1 / 38 workflows

[srimanob]

Close this PR as agreed with Sunanda. I will split it.