grt: implement resistance-aware for CUGR

[eder-matheus]

Summary

Implement resistance-aware cost to CUGR routing flow.

Type of Change

• New feature
• Breaking change

Impact

When using -resistance_aware flag, CUGR now responds with computing costs and prioritizing nets, in order to prioritize low-resistance metal layers for long, high fanout, critical nets. The core logic tries to mimic how FastRoute handles resistance aware, but the costs are mainly applied to the PatterRoute stages.

New unit tests were added for validation. CI is running.

Verification

• I have verified that the local build succeeds (./etc/Build.sh).
• I have run the relevant tests and they pass.
• My code follows the repository's formatting guidelines.

• I have included tests to prevent regressions.
• I have signed my commits (DCO).

[gemini-code-assist]

Code Review

This pull request implements a resistance-aware routing feature in the CUGR global router, allowing critical nets to be biased toward lower-resistance upper metal layers. Key changes include calculating wire and via resistance costs, computing resistance-aware net scores, and integrating these costs into pattern routing, alongside several timing and mechanism validation tests. Feedback on these changes highlights opportunities to improve robustness: specifically, finding the first non-zero layer resistance as a reference instead of assuming layer 0 is valid, adding defensive null-checks for the STA network access, and ensuring markResAwareNets early-returns when the critical net percentage is zero to avoid incorrectly marking nets.