debug: print corresponding dlv command

[hyangah]

When using the legacy debug adapter, it's backed by the traditional headless delve debug server and the adapter prints the command used to launch the debug server in DEBUG CONSOLE. The command is particularly helpful because the headless server launch command is almost identical to what users need to use to use dlv cli. When users troubleshoot and want to verify whether it's delve issue rather than the debug adapter, users need to just copy the command for quick check.

After transitioning to the new dlv-dap adapter, the extension launches dlv dap command and that's what's printed in DEBUG CONSOLE. dlv dap can print the relevant launch configuration when logging is enabled, but still this is not as convenient as the exact dlv command.

Consider printing or providing an option to log a corresponding dlv command (and maybe a sequence of commands to reflect extra work dlv dap is doing, e.g. changing to a directory, setting env vars, go build command, etc).

cc @polinasok @suzmue