Feature request: allow user-defined pwd for unit tests

## Environment data
`dotnet --info` output:
VS Code version: **1.58.0**
C# Extension version: **1.23.13**

## OmniSharp log

## Steps to reproduce

1. create a test project: `dotnet new xunit`;
2. check pwd during runtime of any unit test;
3. it shows the pwd is deep inside `bin` folder, which is not expected.

## Expected behavior

The pwd should be in the same folder as the `*.csproj` file.

## Actual behavior

The pwd is deep inside `bin` folder.