ITS: restore previous UPC iteration

[f3sch]

I simplified some parameters into a single one (1:1). Also this correctly 'restores' how the UPC iteration is done.

[shahor02]

Since the mVertParams.size is hardcoded to 2, this means that we will always run 2 iterations?
And since the actual job done by the 2nd iteration is triggered by nvertices(1st iteration) < vertPerRofThreshold, we have no way to disable it, even effectively? Do I miss something?

[f3sch]

No, by default there is only one iteration run, since the ITSVertexerParam.nIterations=1 by default, which triggers capping the mVertParams to only 1. In o2dpg for Pb-Pb we specficially set it nIterations=2.

[alibuild]

Error while checking build/O2/fullCI_slc9 for dd8f6fe at 2026-04-19 17:04:

## sw/BUILD/O2-full-system-test-latest/log
command /sw/slc9_x86-64/O2/slc9_x86-64-slc9_x86-64-local8/prodtests/full-system-test/dpl-workflow.sh had nonzero exit code 1


## sw/BUILD/o2checkcode-latest/log
--
========== List of errors found ==========
++ GRERR=0
++ grep -v clang-diagnostic-error error-log.txt
++ grep ' error:'
grep: error-log.txt: binary file matches
++ GRERR=1
++ [[ 1 == 0 ]]
++ mkdir -p /sw/INSTALLROOT/0972eb49c661c59fcddb1e8d6b1c661f5fe0d5c5/slc9_x86-64/o2checkcode/1.0-local685/etc/modulefiles
++ cat
--

Full log here.