Launch configuration for C/C++ debugging of Ark packages

We could make it much easier to debug native code in a package by providing a launch configuration that would:

• Automatically pick Ark's PID via a command. Ideally would not require executing code in Ark so it's possible to attach to a session that is running code (can be important to figure out why Ark is stuck). So the PID (which is unknown from the parent process) would be sent by Ark on startup and cached on the frontend side.

• Include the Python code implementing formatters for R variables (#7171). This Python code would ideally live in Ark since it would be tightly integrated with internal APIs. It could be sent over to the frontend on startup.

• Set codelldb's execution engine to native? Alternatively we can document that native expressions, such as calls to Ark debugging helpers (#7174), need to be prefixed with \nat in the Watch Pane. See https://github.com/vadimcn/codelldb/blob/master/MANUAL.md#expressions

• Sets escape-non-printables to false, see #7174.

I'm not sure if this configuration should be provided by the R extension (dynamically) or by a usethis function (statically). My hunch is that a dynamic configuration is more convenient.

Start by reading the requirements here and the linked issues #7171 and #7174, then review codelldb's expressions documentation. Compare a dynamic R-extension configuration with a static usethis configuration, including PID and formatter transfer. Done means the ownership choice and the requested launch, formatter, expression, and non-printable settings are defined.