(WIP) Add support for global runtime and ASP.NET Core installation

[JakeRadMSFT]

(Written by Copilot) Just wanted to try and understand the needed changes.

Summary

Generalizes the global SDK installation infrastructure to also support installing .NET runtimes and ASP.NET Core runtimes globally via a new dotnet.acquireGlobalRuntime command.

Motivation

Extensions like C# Dev Kit need to acquire .NET runtimes globally when a workspace's \global.json\ requires a newer SDK version than the extension's bundled tooling runtime. Currently, only \dotnet.acquireGlobalSDK\ supports global installation. This PR adds the equivalent capability for runtimes and ASP.NET Core runtimes.

Changes

Library (\�scode-dotnet-runtime-library)

• **\GlobalInstallerResolver**: Accept \DotnetInstallMode\ parameter to resolve runtime/aspnetcore installer URLs from the releases JSON (previously hardcoded to SDK)
• **\IGlobalInstaller**: Add \installGlobal()/\uninstallGlobal()/\getExpectedGlobalDotnetPath()\ with backward-compatible default implementations that delegate to existing SDK methods
• **\LinuxGlobalInstaller**: Accept mode parameter, use generalized \ValidateAndInstall/\Uninstall\ methods
• **\LinuxVersionResolver**: Add generalized \ValidateAndInstall(version, mode)/\Uninstall(version, mode)\ methods (existing SDK methods now delegate to these)
• **\WinMacGlobalInstaller**: Accept mode parameter, skip SDK-specific Windows conflict check for runtime installs, handle mode-specific uninstall directories on macOS
• **\DotnetCoreAcquisitionWorker**: Add \�cquireGlobalRuntime()/\�cquireGlobalASPNET()\ methods, pass mode to installer constructors, use generalized install methods in \�cquireGlobalCore\
• **\IDotnetCoreAcquisitionWorker**: Add \�cquireGlobalRuntime/\�cquireGlobalASPNET\ interface methods

Extension (\�scode-dotnet-runtime-extension)

• Register \dotnet.acquireGlobalRuntime\ command supporting both
  untime\ and \�spnetcore\ modes (via \commandContext.mode)

API Usage

\\ ypescript
// Install a .NET runtime globally
const result = await vscode.commands.executeCommand('dotnet.acquireGlobalRuntime', {
version: '9.0.0',
requestingExtensionId: 'ms-dotnettools.csdevkit',
mode: 'runtime', // or 'aspnetcore'
installType: 'global'
});
\\

Backward Compatibility

• All existing SDK methods (\installSDK, \uninstallSDK, \getExpectedGlobalSDKPath) are preserved and now delegate to the new generalized methods
• \GlobalInstallerResolver\ defaults to 'sdk'\ mode when no mode is specified
• No breaking changes to existing API contracts