Fix onprogress not firing when Content-Length is not available for XMLHttpRequest

[BadLice]

Summary:

When an XMLHttpRequest is performed, the onprogress event it is not invoked when the Content-Length header is missing in the response. This is the case when we are calling an endpoint that responds with transfer-encoding: chunked (https://tools.ietf.org/html/rfc9112#section-7.1), preventing the user to keep track of the progress while the server is sending chunks. Despite we will never know the total length of the content (because it will not be known due to the RFC specification, so it will be always -1), we will now be able to keep track of the loaded data.

Note that in Android, this is the current default behaviour.

To address this issue:

• I removed the condition where the downloadProgressBlock was dispatched only when response.expectedContentLength was greater than 0
• I created a new test case for XMLHttpRequest in the tester app to download a chunked file

Changelog:

[IOS] [CHANGED] - fire onprogress event for XMLHttpRequest even when the Content-Length header is missing in the response headers

Test Plan:

before	after
https://github.com/facebook/react-native/assets/37150312/6da3518f-eed3-4808-a2f8-abe26e5c7487	https://github.com/facebook/react-native/assets/37150312/ed1da300-dcf7-4874-a941-a2289f1cb777

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[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	20,364,763	+492
android	hermes	armeabi-v7a	n/a	--
android	hermes	x86	n/a	--
android	hermes	x86_64	n/a	--
android	jsc	arm64-v8a	23,569,643	+112
android	jsc	armeabi-v7a	n/a	--
android	jsc	x86	n/a	--
android	jsc	x86_64	n/a	--

Base commit: b8f1b92
Branch: main

[facebook-github-bot]

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

[facebook-github-bot]

@NickGerleman merged this pull request in 457d14b.

[github-actions]

This pull request was successfully merged by alicata in 457d14b.

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