feat(cross): bundle in-tree libs into the .deb and deploy it over SSH

[jwinarske]

Description

--deb assumed a single self-contained binary. For a project whose executable loads its own shared objects (e.g. a server that links libFooServer.so/libFooRecorder.so built from the same tree), the resulting package shipped only the executable and was not runnable on the target.

• package.bundle_libs — when set, --deb walks the binary's DT_NEEDED closure and ships the in-tree .so files under /usr/lib/<multiarch>/ (a default loader path, so no rpath is needed). Sysroot/system libraries are excluded and remain the caller's depends:. Reuses _stageLinkedLibs, already used for runnable app bundles.
• --deploy for --deb — was gated on --app; now also scp's the package to <user@host> and installs it with apt-get, which resolves Depends: from the device's own repositories.

Validated against an aarch64 Raspberry Pi (Debian trixie): the package installs, apt-get pulls the declared runtime Depends, and the binary runs from /usr/bin with all .sos resolved from system paths (no LD_LIBRARY_PATH).

Adds PackageSpec.fromMap coverage for bundle_libs. dart analyze --fatal-infos --fatal-warnings and the test suite pass.

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore