fix stopOnEntry

[jhendrixMSFT]

Send a dummy thread to vscode when stopped on entry as there are no
threads in the process yet.
Send the stop event with the same dummy thread ID.

[jhendrixMSFT]

Fixes #763

[ramya-rao-a]

cc @quoctruong

[quoctruong]

LGTM. Does this work with remote attach scenario?

[jhendrixMSFT]

Good question, I tried it and it doesn't work. While I'm sure it can be fixed, I want to ask if we think this scenario is valuable? If not then I suggest removing stopOnEntry from the attach option.
I personally feel like this isn't really useful and in my experience I don't recall other debuggers doing this. However I might be overlooking some use case.

[quoctruong]

Yes, I think by default, the program for remote attach scenario wouldn't start until a debugger is connected to it anyway. Therefore, this option may not be needed for that.

[jhendrixMSFT]

@ramya-rao-a are you ok with removing stopOnEntry from attach?

[ramya-rao-a]

@jhendrixMSFT Yes, I am fine with removing stopOnEntry for attach scenarios and ignore it for the launch request in debug mode as well