Include moat circumvention countries in the build (tor-browser-build part)

This is the tor-browser-build complement to tor-browser#43463 (closed).

@pierov can you set up tor-browser-build to add a list of countries at some chrome path, like pt_config.json. I'm not sure of the best way to do this myself.

I'll assign tor-browser#43463 (closed) to myself to get tor-browser to read this file.

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