process: allow StartExecution() to take a main script ID
The idea is to allow the C++ layer to run arbitrary scripts as the main script. This paves the way for
- cctest of the execution of Node.js instances
- Earlier handling of per-process CLI options that affect execution modes (those usually do not make sense for the embedders).
- Targets like mkcodecache or mksnapshot.
Also moves the handling of _third_party_main.js
into C++.
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
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