[hist] extend LIST option to support CONT1 CONT2 CONT3

[ferdymercury]

This Pull request:

Changes or fixes:

fyi @bgrube

Fixes #20858

Follow-up of d4b273b

Checklist:

• tested changes locally
• updated the docs (if necessary)

[couet]

The LIST option retrieves the contours generated by the CONT0 option. I am not sure the other algorithms work the same way as CONTO and therefore the contours might not be generated as CONTO does it.

[ferdymercury]

I verified that it works with this test script:

   auto c1 = new TCanvas("c1","c1",600,400);
   auto hcont1 = new TH2F("hcont1","Option CONT1Z LIST example ",40,-4,4,40,-20,20);
   float px, py;
   for (Int_t i = 0; i < 25000; i++) {
      gRandom->Rannor(px,py);
      hcont1->Fill(px-1,5*py);
      hcont1->Fill(2+0.5*px,2*py-10.,0.1);
   }
   hcont1->Draw("CONT1Z LIST");
   gPad->Update();
   new TCanvas();
    ((TGraph*)((TList*)((TObjArray*)gROOT->GetListOfSpecials()->FindObject("contours"))->At(0))->First())->Draw("AL");

[couet]

Ok LGTM

[github-actions]

Test Results

    22 files      22 suites   3d 14h 26m 4s ⏱️
 3 813 tests  3 813 ✅ 0 💤 0 ❌
76 915 runs  76 915 ✅ 0 💤 0 ❌

Results for commit 4dc9352.