Add support for running DebugConfigurations with serverReadyAction (#197597)

* Add support for running DebugConfigurations with serverReadyAction

This PR adds 'config' as an option for serverReadyAction. It runs
similar to 'name', but if a configuration is generated on the fly, its
easier to inject the debug configurations with the serverReadyAction.

* Merge into startDebugSession method

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Co-authored-by: Rob Lourens <[email protected]>