[GCC flags] enable -Wconversion flag

[smuzaffar]

as requested cms-sw/cmssw#39098
lets test it for full cmssw to see how many such warnings are there.

[cmsbuild]

A new Pull Request was created by @smuzaffar (Malik Shahzad Muzaffar) for branch IB/CMSSW_12_5_X/master.

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

[smuzaffar]

test parameters:

• full_cmssw = true

[smuzaffar]

please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-7f08a7/26906/summary.html
COMMIT: 5380f86
CMSSW: CMSSW_12_5_X_2022-08-17-2300/el8_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmsdist/8027/26906/install.sh to create a dev area with all the needed externals and cmssw changes.

The following merge commits were also included on top of IB + this PR after doing git cms-merge-topic:

• @nurfikri89 [JMENanoAOD] Updates for Run-3 cmssw#39000
• @ChrisMisan Fix PPSDiamondDQM histogram of rechits in the last lumisection cmssw#39076
• @atsatsos97 DQM for DiPhoton Paths in EXO/HIG PAGs cmssw#39093

You can see more details here:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-7f08a7/26906/git-recent-commits.json
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-7f08a7/26906/git-merge-result

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 2 differences found in the comparisons
• DQMHistoTests: Total files compared: 51
• DQMHistoTests: Total histograms compared: 3692140
• DQMHistoTests: Total failures: 7
• DQMHistoTests: Total nulls: 1
• DQMHistoTests: Total successes: 3692110
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 975.5440000000001 KiB( 50 files compared)
• DQMHistoSizes: changed ( 11634.0,... ): 108.078 KiB HLT/EXO
• DQMHistoSizes: changed ( 11634.0,... ): 54.512 KiB HLT/HIG
• DQMHistoSizes: changed ( 312.0 ): 0.004 KiB MessageLogger/Warnings
• Checked 212 log files, 49 edm output root files, 51 DQM output files
• TriggerResults: no differences found

[smuzaffar]

closing it for now. we can reopen if needed