Update externals/install-dotnet.ps1 and externals/install-dotnet.sh to
the v2026.05.19 release of dotnet/install-scripts. This uptakes the
changes from dotnet/install-scripts#697 which preserves archive links
during installation (hardlinks on Windows, symlinks on Linux) as part
of dotnet/sdk#52182.
On Windows, .NET 11.0+ is now installed via tar.gz archives which
preserves hardlinks, significantly reducing disk space usage.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
