* service/dap: use specified working directory for launch requests

If a user specifies a working directory in the launch request,
then the process should use that working directory. This may
affect how the program runs and the user should be able to have
control over this.

* service/dap: add tests for launch with working dir

Added tests to make sure the working directory is set correctly.

* service/dap: fix TestWorkingDir on windows

* service/dap: use %q to print quoted string

* cmd/dlv: update dap warning about working dir

* service/dap: change the launch argument to be wd`

* update warning to specify only launch request