drt: initMazeCost_ap_helper refactor

[openroad-ci]

Summary

the initMazeCost_ap_helper is verbose and has a lot of unnecessary indentation. I mostly moved things around and applied guards when possible. The function does the exact same thing.

Clang-format made some changes by itself when I fed it through the file.

I also used the reverse() function inside the correct() function and eliminated correctU() as it was completely equivalent to correct() in every context it was called.

Type of Change

• Refactoring

Impact

No functional behavior changed

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 signed my commits (DCO).

Related Issues

#9850

[gemini-code-assist]

Code Review

This pull request refactors initMazeCost_ap_helper in FlexDR_init.cpp to improve readability through early exits and consolidated logic. In FlexGridGraph.h, the correctU method was replaced with a more general correct function. Feedback suggests replacing a std::cout warning with a proper logger error call when failing to find grids for marker costs to ensure critical failures are not missed.

[gemini-code-assist]

Unexpected failures during the routing flow, such as failing to find grids to add marker cost, should be logged as an error instead of a warning. This ensures that critical failure messages are not missed by the user. Additionally, avoid manual formatting changes and rely on the logger's standard output.

Suggested change

	std::cout << "Warning: marker bloat 4x width but could not find "
	"two grids "
	"to add marker cost\n";
	logger->error(utl::DRT, 1000, "marker bloat 4x width but could not find two grids to add marker cost");

References

1. Unexpected failures during the routing flow, such as failing to generate a Steiner tree, should be logged as an error, not a warning. This ensures the end user does not miss critical failure messages.
2. Rely on clang-format for code formatting instead of applying manual style changes.

[bnmfw]

@maliberty I sometimes find these kinds of "internal DRT errors" which look obsolete/legacy to me, should we transform them into actual error or get rid of them?

[maliberty]

Transform them unless you are certain they can't happen.

[github-actions]

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