Debug Adapter Host doesn't properly support adapters that send 'initialized' event before 'launch' request

[andrewcrawley]

The debug adapter host currently waits for both the initialize and launch requests to complete before sending breakpoints, exception settings, etc. This causes problems with adapters like Mock Debug, which expect breakpoints to be set before launching, resulting in missed breakpoints and other similar issues.

Adapters which send the initialized event as part of their launch request processing (e.g. node2, vsdbg, etc) are unaffected.

The host should be fixed to work like VS Code, sending breakpoints and other configuration information as soon as the initialized event is received, rather than waiting until after the launch request has been processed.