fix: Gap translations in Blueprint Helper (#3027)

Introducing small changes into the way translations are handled in the `BlueprintHelper` gap filling. 

Previously, because the rotation of a gap volume was applied before the translation, the gaps were positioned in the wrong points of the global coordinates. This was due to the fact that `negC` and `posC` are already defined in the rotated frame. The change solidifies the global way of defining the transformations in the user code, which seems to be consistent with the way it is handled across the `Blueprint`. 
 
To give an example: if the user code tries to fill the gaps in the detector rotated by `pi/2`, the `negC`, `posC` would've been calculated along the already rotated axis. Then, the gap transformation would've been constructed and the filling volume would've been sent along the `pi` with respect to the initial global coordinates, as the rotation would've been effectively applied twice. Now, the fact that the rotation is already present in the translation vector is taken into account.

Core/src/Detector/detail/BlueprintHelper.cpp

@@ -131,7 +131,7 @@ void Acts::Experimental::detail::BlueprintHelper::fillGapsCylindrical(
         auto gapName = node.name + "_gap_" + std::to_string(igap);
         auto gapTransform = Transform3::Identity();
         gapTransform.rotate(node.transform.rotation());
-        gapTransform.translate(0.5 * (neg + negC));
+        gapTransform.pretranslate(0.5 * (neg + negC));
         auto gap = std::make_unique<Blueprint::Node>(
             gapName, gapTransform, VolumeBounds::eCylinder,
             std::vector<ActsScalar>{cInnerR, cOuterR, 0.5 * gapSpan});
@@ -148,7 +148,7 @@ void Acts::Experimental::detail::BlueprintHelper::fillGapsCylindrical(
       auto gapName = node.name + "_gap_" + std::to_string(igap);
       auto gapTransform = Transform3::Identity();
       gapTransform.rotate(node.transform.rotation());
-      gapTransform.translate(0.5 * (negC + posC));
+      gapTransform.pretranslate(0.5 * (negC + posC));
       auto gap = std::make_unique<Blueprint::Node>(
           gapName, gapTransform, VolumeBounds::eCylinder,
           std::vector<ActsScalar>{cInnerR, cOuterR, 0.5 * gapSpan});
@@ -237,17 +237,13 @@ void Acts::Experimental::detail::BlueprintHelper::fillGapsCuboidal(
   unsigned int igap = 0;
   for (auto& child : node.children) {
     auto [neg, pos] = endPointsXYZ(*child, binVal);
-    if (neg[binVal] < negC[binVal]) {
-      throw std::runtime_error("BlueprintHelper: Overlap detected for child '" +
-                               child->name + "' of node '" + node.name + "'");
-    }
     ActsScalar gapSpan = (neg - negC).norm();
     if (gapSpan > s_onSurfaceTolerance) {
       // Fill a gap node
       auto gapName = node.name + "_gap_" + std::to_string(igap);
       auto gapTransform = Transform3::Identity();
       gapTransform.rotate(node.transform.rotation());
-      gapTransform.translate(0.5 * (neg + negC));
+      gapTransform.pretranslate(0.5 * (neg + negC));
       std::vector<ActsScalar> gapBounds{0, 0, 0};
       gapBounds[binVal] = 0.5 * gapSpan;
       for (auto bv : allowedBinVals) {
@@ -270,7 +266,7 @@ void Acts::Experimental::detail::BlueprintHelper::fillGapsCuboidal(
     auto gapName = node.name + "_gap_" + std::to_string(igap);
     auto gapTransform = Transform3::Identity();
     gapTransform.rotate(node.transform.rotation());
-    gapTransform.translate(0.5 * (negC + posC));
+    gapTransform.pretranslate(0.5 * (negC + posC));
     std::vector<ActsScalar> gapBounds{0, 0, 0};
     gapBounds[binVal] = 0.5 * gapSpan;
     for (auto bv : allowedBinVals) {