Refactor the debug launch configuration resolvers

[andyleejordan]

Some much needed TLC, especially now that VS Code with resolve its predefined variables used in configurations.

Do not set cwd for debug launch configurations

Instead, respect it if it exists, and otherwise consistently do not change it. Debugging will run in the session's current cwd, or if and only if the user set cwd on the launch config will it change.

Resolves #4082. My own testing seems to indicate this works well and as expected (consistently). However, I suspect we'll get some complaints when it rolls out.