Initial version of .NET Solution Launcher

Startup project and solution configuration (Debug|x64, Test|x64, ...) in
the status bar, with build and debug tasks that pass both configuration
and platform. Made for DotRush, whose build never passes -p:Platform and
whose status item shows the configuration but not the project.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0169iPWwKHZoBTNN9qwXiwqk

.vscodeignore

@@ -0,0 +1,8 @@
+.vscode/**
+.vscode-test/**
+src/**
+out/test/**
+tsconfig.json
+**/*.map
+.gitignore
+package-lock.json