Add HiGHS solver to rebalancer OSS build via getdeps

Summary:
Create a highs-optimizer getdeps manifest so that HiGHS is automatically
available when building rebalancer via getdeps.py. This enables OSS
developers to run rebalancer tests that require a MIP solver.

The manifest is hybrid: builds HiGHS v1.13.1 from source on platforms
without system packages (Ubuntu 24.04 CI, CentOS), and uses system
packages where available (Fedora, Debian Trixie, macOS Homebrew).

Regenerated GitHub Actions workflow files to include the new dependency.

Reviewed By: sahilsd

Differential Revision: D99356524

fbshipit-source-id: d12fe75072cd949be3d8f8bceb9143fd1c72eb9c

Author: r-barnes

build/fbcode_builder/manifests/highs-optimizer

@@ -0,0 +1,25 @@
+[manifest]
+name = highs-optimizer
+
+[git]
+repo_url = https://github.com/ERGO-Code/HiGHS.git
+rev = v1.13.1
+
+[build]
+builder = cmake
+
+[cmake.defines]
+BUILD_TESTING = OFF
+BUILD_EXAMPLES = OFF
+FAST_BUILD = ON
+
+[rpms]
+coin-or-HiGHS
+coin-or-HiGHS-devel
+
+[debs]
+highs
+libhighs-dev
+
+[homebrew]
+highs

build/fbcode_builder/manifests/rebalancer

@@ -23,6 +23,7 @@ folly
 gflags
 glog
 googletest
+highs-optimizer
 xxhash
 
 [dependencies.os=linux]