Gui: 3DBX fix ruler

[LucasYuki]

Closes issue #9089

Changes:

• Adds the method LayoutViewer::getChips().
  • Return all dbChip and dbChipInst.
• Iterate through all blocks instead of using getBlock().
• LayoutViewer::searchNearestViaEdge does the search using the block coordinates:
  • Transform the search variables to the current block coordinate system.
  • After searching the block, turn back the search variables to the global coordinate system.

[gemini-code-assist]

Code Review

The pull request addresses issue #9089 by refactoring the ruler functionality to correctly handle multiple blocks within the layout. The changes involve iterating through all chip_insts and performing searches within each block's coordinate system. The getBounds function now correctly merges bounding boxes and die areas from all blocks, applying necessary transformations. The searchNearestViaEdge and selectViaShapesAt functions have been updated to accept a dbBlock* parameter, allowing them to operate within the context of a specific block. The review comments highlight a critical issue with coordinate transformations that could lead to incorrect results when handling closest_edge across different blocks.

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[maliberty]

This PR does not work for me

• The measurements seem to always be in dbu regardless of Options->Show DBU.
• It won't snap to a second die.

I tested with openroad -gui read_3dbx.tcl and

diff --git a/src/odb/test/data/example.3dbx b/src/odb/test/data/example.3dbx
index ef4a84dfb7..eb0617ad62 100644
--- a/src/odb/test/data/example.3dbx
+++ b/src/odb/test/data/example.3dbx
@@ -30,7 +30,7 @@ Stack:
     z: 0.0
     orient: R0
   soc_inst_duplicate:
-    loc: [100.0, 200.0]
+    loc: [100.0, 1300.0]
     z: 300.0
     orient: MZ

and couldn't snap to the upper die at all.