chore: vendor DreamPlace dependencies

[zhaoxueyan1]

Summary

• Replace DreamPlace recursive Git submodules with tracked source snapshots.
• Include all third-party build inputs in source distributions.
• Remove recursive submodule setup from CI, release, Nix, and documentation.

Verification

• Built the source distribution and verified its vendored source contents.
• Configured an independent source tree without Git metadata.
• Built and imported place_io_cpp and independent_set_matching_cpp with the project ABI.

The root editable rebuild is not listed as passing: this host combines the Nix compiler runtime with host COIN headers/libraries, which reaches an existing Lemon pthread ABI conflict.

[Copilot]

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[Emin017]

So many files...