If possible, enable caching of VM responses between different runs of the debugger for the same app

Currently, the debug service port might change between different runs of the debugger for the same app run, so REST API caching would not work.

Make sure we use the same port if possible and ensure that caching is done on VM responses when possible.

The issue names no files or tests; start by tracing how the debugger assigns its debug service port and handles VM REST responses across runs of the same app. Check whether the port can be reused safely, then verify that VM responses are cached when possible and that separate app runs do not share invalid data.

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