Reset pixel segments collection at start

[ariostas]

The pixel segments collection was not being reset, so it was causing some issues. I'm surprised that it was only noticeable on GPU and not on CPU.

@GNiendorf could you verify that this fixes the issue?

[GNiendorf]

Just checked this PR, the performance plots look good now. Memory usage looks unchanged with/without this fix. Thank you again for finding this

[slava77]

/run all

[slava77]

I think that this can go upstream directly.

[github-actions]

The PR was built and ran successfully in standalone mode. Here are some of the comparison plots.

The full set of validation and comparison plots can be found here.

Here is a timing comparison:

   Evt    Hits       MD       LS      T3       T5       pLS       pT5      pT3      TC       Reset    Event     Short             Rate
   avg     32.5    381.6    187.6    150.8    166.7    707.9    132.4    237.1    179.0      1.7    2177.2    1436.8+/- 406.3     577.1   explicit[s=4] (target branch)
   avg     29.1    382.0    190.4    151.9    145.9    622.9    129.8    236.0    167.3      1.9    2057.3    1405.2+/- 386.2     545.8   explicit[s=4] (this PR)

[github-actions]

The PR was built and ran successfully with CMSSW. Here are some plots.

OOTB All Tracks

The full set of validation and comparison plots can be found here.