Unblocks dotnet/dotnet#176

Commit 1: Infra improvements that makes it easier to enable inner clone directly in SBE

• Build the tasks project as a dependency of the repo-projects and remove the serial build step in Build.props
• Let the task project use the Arcade SDK and remove Arcade conditions from D.B files as it's always imported now.
• Convert the task project's use of Newtonsoft.Json to System.Text.Json (thanks Copilot).
• Remove a ton of dead properties, items and targets
• Use the Microsoft.Build.NoTargets SDK in repo-projects projs (same as in the VMR) and define a dependency for it in global.json.
• Remove reading the SDK version in build.sh and just read from the MSBuild property instead.
• Make all repo-projects logging (binlogs + logs) go under artifacts\log\<config>\<repo>\ (same as in VMR)
• Clean-up the semaphore infra for incremental builds by following the VMR model
• Use standard Arcade.Sdk properties for DotNetTool and DotNetRoot

Commit 2: Enable inner-clone functionality in SBE and disable the ArPow UseInnerClone infra.

Instead of a clone of the entire SBE repository, clone the inner repos directly. The cloned repo folder is located under src\<repo>\artifacts\clone\.

I validated that after this change the produced packages still get correctly published under the ArtifactsShippingPackagesDir and the log files under the ArtifactsLogDir.