[typescript] use built-in abortsignal

[davidgamero]

update @types/node from 12 to 16.

considering the current node LTS is 22, it would be helpful to enable using newer built-in types over older polyfill-based solutions without jumping too many versions at once to catch upgrade issues

i've added an explicit version of @types/node in favor of *, but would appreciate feedback on if that's a good idea

@types/node was pinned to node 12 by previous peer dependency on node-fetch 2.6.0, upgrading to 2.7.0 allows us to use the AbortSignal built-in type

update form-data to match version from #21748 in default tests

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