[10.6.X] Correctionlib C++ and python2 binding

[nsmith-]

This uses a special Makefile rather than pip because the normal package is python3-only. This build has the C++ evaluator and python2 bindings only. A subset of the high-level wrapper could be backported as well, in principle.

TODO: in my test area, the python2 binding is not available until I run the corresponding ...build/slc7_amd64_gcc700/external/correctionlib/2.1.0-3822e3561f9af87ea18bc53317ea8ebf/etc/profile.d/init.sh. Is there anywhere else I have to add the site package since I am not pip installing in cmsdist? For reference, a sufficient python2 test would be:

import correctionlib._core as cc
cs = cc.CorrectionSet.from_file("/cvmfs/cms.cern.ch/rsync/cms-nanoAOD/jsonpog-integration/POG/EGM/2017_UL/photon.json.gz")
cs["UL-Photon-ID-SF"].evaluate("2017", "sf", "Loose", 1.2, 25.3)

Closes #7510

[cmsbuild]

A new Pull Request was created by @nsmith- (Nicholas Smith) for branch IB/CMSSW_10_6_X/gcc700.

@cmsbuild, @smuzaffar, @iarspider, @ddaina can you please review it and eventually sign? Thanks.
@perrotta, @dpiparo, @qliphy you are the release manager for this.
cms-bot commands are listed here

[nsmith-]

In future releases, the special Makefile will be in the regular release and we can drop the cms0 suffix here.

[cmsbuild]

Pull request #7523 was updated.

[smuzaffar]

please test with cms-sw/cmssw#36547

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-5b2713/21586/summary.html
COMMIT: d3f4106
CMSSW: CMSSW_10_6_X_2022-01-09-0000/slc7_amd64_gcc700
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmsdist/7523/21586/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: 2 differences found in the comparisons
• DQMHistoTests: Total files compared: 35
• DQMHistoTests: Total histograms compared: 3215686
• DQMHistoTests: Total failures: 2
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3215350
• DQMHistoTests: Total skipped: 334
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 34 files compared)
• Checked 143 log files, 29 edm output root files, 35 DQM output files
• TriggerResults: no differences found

[smuzaffar]

+externals
@perrotta @qliphy . feel free to merge this along with cms-sw/cmssw#36547 for 10.6.X

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next IB/CMSSW_10_6_X/gcc700 IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @perrotta, @dpiparo, @qliphy (and backports should be raised in the release meeting by the corresponding L2)

[qliphy]

+1