break at main option when launching

CDT (Eclipse IDE version) has a "break at main" (with a configurable symbol) option. GDB itself has a `start` method that will do that functionality automatically and can be accessed via MI with `-exec-run --start`.

This is a feature request to add that.

In the meantime the workaround is `"initCommands": ["tbreak main"]` for launch scenario.

Start by tracing how the launch scenario handles GDB/MI execution and compare it with the issue's suggested `-exec-run --start` command. Done means the launch option supports breaking at the configurable main symbol without requiring the `initCommands` workaround.

Written by the indexing model from the issue text.