Fix FormData to properly handle appended arrays.

[bang9]

Summary

The Array appended to FormData must be transmitted in the form of a string.
However, it is treated as a file object and transmitted, because typeof Array is 'object' too

In network

form.append('array_name', ['a', 'b', 'c'])

// Browser
// --
// content-disposition: form-data; name='array_name';
//
// a,b,c
// --

// ReactNative
// --
// content-disposition: form-data; name='array_name';
// 
// 
// --

Changelog

[General] [Fixed] - The Array appended to FormData is transmitted as a string

Test Plan

Added test case

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: 725bffc
Branch: main

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	8,291,388	+25
android	hermes	armeabi-v7a	7,625,109	+48
android	hermes	x86	8,764,225	+46
android	hermes	x86_64	8,700,779	+39
android	jsc	arm64-v8a	9,679,731	+0
android	jsc	armeabi-v7a	8,670,129	+12
android	jsc	x86	9,638,059	+1
android	jsc	x86_64	10,232,228	+2

Base commit: 725bffc
Branch: main

[facebook-github-bot]

@charlesbdudley has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[bang9]

Hi @charlesbdudley
Is there anything else I can do help to this PR get merged? :)

[react-native-bot]

This pull request was successfully merged by @bang9 in d2e8e7d.

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