Complete HiGHS v1.12.0 integration and fix references

[PedramHooshangiAUGAI]

This pull request adds support for the HiGHS solver throughout the codebase, updating dependencies, build configurations, and solver selection logic. The main changes ensure that HiGHS can be used for mixed integer programming, particularly in the Christofides algorithm, and that the build system recognizes and configures HiGHS correctly.

Support for HiGHS solver:

• Added HiGHS as an option for minimum weight matching with MIP in ChristofidesPathSolver, including updates to relevant enums, solver selection logic, and conditional compilation checks in ortools/graph/christofides.h. [1] [2] [3] [4]

Build system and configuration updates:

• Updated MODULE.bazel to use HiGHS version 1.12.0, ensuring the latest features and bug fixes are available.
• Added USE_HIGHS to build configuration files (or-tools.code-workspace and makefiles/Makefile.cpp.mk) so the build system recognizes and configures HiGHS. [1] [2]

Examples and interface improvements:

• Enabled HiGHS solver in the uncapacitated facility location example, allowing users to run integer programming examples with HiGHS.
• Updated HighsInterface to reference HiGHS instead of PDLP in comments and version strings, clarifying solver identity and improving maintainability. [1] [2]<!--
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[lperron]

Hi,

can you rebase vs main. A few changes have landed after stable was updated.

[PedramHooshangiAUGAI]

Hi,

can you rebase vs main. A few changes have landed after stable was updated.

Hi, not sure if I am able to do that, the repository has rules preventing the push

[PedramHooshangiAUGAI]

Hi,
can you rebase vs main. A few changes have landed after stable was updated.

Hi, not sure if I am able to do that, the repository has rules preventing the push

By the way, the rebase has too many conflicts due to the large differences between my branch and main