Handle DXF files with out of bounds values

First, ensure that we calculate the bbox of the imported elements.

If the total BBOX is outside our allowed value, refused to import.  This
needs to be scaled or addressed in an external editor

If the bbox fits, then make sure that we clamp it such that the largest
element is still within our bounds

Fixes https://gitlab.com/kicad/code/kicad/-/issues/18523

(cherry picked from commit a724b3d8b1)

common/commit.cpp

@@ -162,6 +162,9 @@ void COMMIT::makeEntry( EDA_ITEM* aItem, CHANGE_TYPE aType, EDA_ITEM* aCopy, BAS
     ent.m_copy = aCopy;
     ent.m_screen = aScreen;
 
+    // N.B. Do not throw an assertion for multiple changed items.  An item can be changed multiple times
+    // in a single commit such as when importing graphics and grouping them.
+
     m_changedItems.insert( aItem );
     m_changes.push_back( ent );
 }