Digitization: Return to Poisson event time distribution for main run_digi macro

The Uniform time distribution was introduced in !1204 (merged), with the intend to be a debug option, as stated in the MR.
It is clearly unrealistic and the default should be changed to Poisson in the 'official' macro.

Related to #1792

assigned to @v.friese

Dear @f.uhlig, @p.-a.loizeau,

you have been identified as code owner of at least one file which was changed with this merge request.

Please check the changes and approve them or request changes.

added CodeOwners label

added BugFix label

changed title from Digitization: Return to Poisson event time distribution to Digitization: Return to Poisson event time distribution for main run_digi macro

requested review from @v.friese

approved this merge request

added 15 commits

• abbe4287...10a8de1d - 14 commits from branch computing:master
• 860b46bc - return to Poisson time distribution for digitization

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merged

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