Use fetch client settings object for fetching submodules

[hiroshige-g]

Previously, fetch client settings object of internal module script graph fetching procedure is used for the top-level module script but not submodules, because module script's settings object (which is module map settings object of internal module script graph fetching procedure) is passed in Step7 of fetch the descendants of a module script.

This PR uses fetch client settings object also for submodules, by adding fetch client settings object argument to fetch the descendants of a module script, and plumbing it to internal module script graph fetching procedure and from callers.

Fixes #3757.

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/links.html ( diff )
/scripting.html ( diff )
/webappapis.html ( diff )

[domenic]

Great find, thank you!