Add support for collecting dumps on crash

[dibarbet]

This adds an option to easily capture a crash dump of the language server process.

1. A vscode option is generally easier than manually trying to launch vscode with a specific set of environment variables
2. There have been a couple reports where manually setting the env vars isn't easy to do (for example wsl where the code server process is not directly launched by the user) - e.g. [BUG] Workspace update handlers close due to JSON-RPC connection lost microsoft/vscode-dotnettools#522

[jasonmalinowski]

You might want to comment what the substitutions do here, especially because I don't see what %d does in the docs. Did you mean %p?

[dibarbet]

Ah %d is the old one, see https://github.com/dotnet/runtime/blob/main/docs/design/coreclr/botr/xplat-minidump-generation.md#configurationpolicy

I'll add a comment and change to %p