DPL: investigate increase in displacement after auto detection to disallow 1-site gaps

[eder-matheus]

Describe the bug

After merging PR #6718, some private designs had a increase in the displacement in the detailed placement stage. However, the 1-site gaps were avoided even without the disallow 1-site gaps flags, so it's possible that DPL is making unnecessary movements to avoid 1-site gaps.

A possible reason for that is that the placement padding might be considered when avoiding 1-site gaps, which is too pessimistic.

Expected Behavior

The displacement should not increase that much, ideally not changing at all when comparing with previous versions of OpenROAD.

Environment

Secure-CI

To Reproduce

Internal testcase.

Relevant log output

Screenshots

No response

Additional Context

No response