dotnet format forwarding is broken with aot

[tmds]

$ dotnet format --help
The application to execute does not exist: '/tmp/dotnet-ms/DotnetTools/dotnet-format/dotnet-format.dll'

This probably regressed when enabling native aot.

FormatForwardingApp uses AppContext.BaseDirectory to locate dotnet-format.dll:

sdk/src/Cli/dotnet/Commands/Format/FormatForwardingApp.cs

Lines 13 to 20 in 3b1207f

	private static string GetForwardApplicationPath()
	=> Path.Combine(AppContext.BaseDirectory, "DotnetTools/dotnet-format/dotnet-format.dll");
	private static string GetDepsFilePath()
	=> Path.Combine(AppContext.BaseDirectory, "DotnetTools/dotnet-format/dotnet-format.deps.json");
	private static string GetRuntimeConfigPath()
	=> Path.Combine(AppContext.BaseDirectory, "DotnetTools/dotnet-format/dotnet-format.runtimeconfig.json");

The fix should be to use SdkPaths.SdkDirectory instead of AppContext.BaseDirectory as described in:

sdk/.github/skills/add-dotnet-aot-command/SKILL.md

Lines 71 to 101 in 3b1207f

	## Resolving the versioned SDK root (do NOT use BCL path APIs)
	The muxer loads `dotnet-aot.dll` directly from the versioned SDK directory (e.g. `.../sdk/11.0.100/`),
	but inside that process the BCL "where am I" APIs do **not** point there:
	- `AppContext.BaseDirectory`, `Environment.ProcessPath`, `Process.GetCurrentProcess().MainModule` -> the
	**muxer / install root**.
	- `Assembly.Location` -> the **empty string** (ILC hard-errors with `IL3000`).
	So deriving an SDK-relative path (`MSBuild.dll`, `Sdks/`, `DotnetTools/`, targets) from
	`AppContext.BaseDirectory` or a dll path is **wrong** in the AOT bubble. Instead:
	- **In-repo:** read `SdkPaths.SdkDirectory` (in `Microsoft.DotNet.Cli.CoreUtils`), which resolves the
	`Microsoft.DotNet.Sdk.Root` AppContext value -> SDK assembly directory -> `AppContext.BaseDirectory`
	(once, cached).
	- `NativeEntryPoint.ExecuteCore` resolves the SDK directory once (host `sdk_dir`, else self-locating the
	`dotnet-aot` module via `SdkRootLocator`) and **publishes it as the `Microsoft.DotNet.Sdk.Root`
	AppContext value** for the compiled-in assemblies.
	- **Out-of-repo code** (MSBuild tasks, NuGet, runtime - no `Cli.Utils` reference) replicates the contract
	inline: read the `Microsoft.DotNet.Sdk.Root` AppContext value first, else the existing BCL logic.
	```csharp
	string sdkDirectory =
	AppContext.GetData("Microsoft.DotNet.Sdk.Root") is string sdkRoot && sdkRoot.Length > 0
	? sdkRoot
	: /* existing logic, e.g. AppContext.BaseDirectory */;
	```
	When bringing a command into AOT, switch any `AppContext.BaseDirectory` / `Assembly.Location` used as
	"the SDK directory" to the above contract. Search current call sites rather than maintaining a static
	list in this skill; update `SdkRootResolution.md` when the contract or ownership changes.

cc @baronfel