Port HTTPRequest gzip compression to 3.4

[tavurth]

Tests are finally passing 🎉

#48581

Edit: Backport of #38944

[tavurth]

@Wavesonics I hope I ported your code faithfully, thank you for the original PR!

[Wavesonics]

Nice, it looks good to me!

[tavurth]

@Calinou sorry to ping you on this, is there something else I should do to push for this in the 3.4 release?

Excited to see this feature speeding up my API calls :)

[akien-mga]

Thanks!

[Faless]

This causes a few regressions including #53085 so it needs to be reverted. The original PR on master #38944 is left for now but will need work if we want to keep in 4.0 (or will need revert too).

Issues:

• Some platform/HTTPClient might not allow those headers (HTML5)
• Response is not decompressed when saved to file.
• We need facilities to decompress a stream (i.e. not decompress all in memory but in chunks to file).

[Wavesonics]

I can put some time in on the master implementation to get it fixed up

[RPicster]

Will this feature be looked into again?
It would be great to have in 3.x.
Could it be eventually solved by not making it automatic but by a parameter?

[tavurth]

@RPicster if we have a working master implementation then this should be pretty trivial to port back to 3.x again.

[Wavesonics]

I'm taking a look at what needs to be done here,

• Some platform/HTTPClient might not allow those headers (HTML5) can you elaborate? Is this a problem with the web export? What would a solution look like? Disable the option to include the header on that export or something?
• Response is not decompressed when saved to file. easy enough, I can implement that
• We need facilities to decompress a stream (i.e. not decompress all in memory but in chunks to file). I think this should be do-able using the new stream decompression I added for this already, I'll look into it.

Other than these 3 issues is there anything else that is needed to consider this fixed?

[Wavesonics]

#55946 addresses the 2nd two points listed above, we can now stream decompress a file to another file (though that is not exposed through GDScript yet.) and that is then used to decompress the downloaded to file option in HttpRequest.

I don't have any idea how we deal with HTML5 as a platform in Godot, so maybe someone could clue me in. It sort of sounds like on HTML5 exports, we should just turn off the "Accept Gzip header" option under the hood or something?