gifsave_buffer: frame too large

[wchaws]

The new GIF saver can only save GIF images smaller than 2000x2000 pixels, see:
https://github.com/libvips/libvips/blob/d9c00eb5ca577018b40533f041230754484ace7e/libvips/foreign/cgifsave.c#L437-L442

kleisauke/net-vips#157

curl https://HOST/upload/2022/06/25/64209978/278cb06fc571ac3cab03e8bfa65ec588_7820959467212072440.gif\?x-oss-process\=image/format,gif/quality,q_80 | exiftool -
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 1589k  100 1589k    0     0  11.8M      0 --:--:-- --:--:-- --:--:-- 11.8M
ExifTool Version Number         : 11.88
File Type                       : GIF
File Type Extension             : gif
MIME Type                       : image/gif
GIF Version                     : 87a
Image Width                     : 2048
Image Height                    : 2048
Has Color Map                   : Yes
Color Resolution Depth          : 8
Bits Per Pixel                  : 8
Background Color                : 0
Animation Iterations            : Infinite
Frame Count                     : 14
Duration                        : 1.54 s
Image Size                      : 2048x2048
Megapixels                      : 4.2

https://HOST/upload/2022/06/14/151782143/cb1517ae88184627a2a9c860de0fd38a_5634428565229009647.gif?x-oss-process=image/format,gif/quality,q_80
https://HOST/upload/2022/06/25/64209978/278cb06fc571ac3cab03e8bfa65ec588_7820959467212072440.gif?x-oss-process=image/format,gif/quality,q_80
https://HOST/upload/2022/06/27/40355445/3a4343b116a0e072c3cf0791e16600c2_1557625664687937150.gif?x-oss-process=image/format,gif/quality,q_80
https://HOST/upload/2022/06/28/25381208/93fc7ec4652204707fe3bb1c3e84757b_4393340964671012177.gif?x-oss-process=image/format,gif/quality,q_80
https://HOST/upload/2022/06/28/25381208/93fc7ec4652204707fe3bb1c3e84757b_4393340964671012177.gif?x-oss-process=image/quality,q_80/format,gif
https://HOST/upload/2022/06/29/77672295/271898bf2ba740b8ea88e6611a870b9b_1726560684206440707.gif?x-oss-process=image/format,gif/quality,q_80

Describe the bug

To Reproduce

Expected behavior

Please complete the following information about the solution:

• Version: [e.g. v1.0.0]
• Region: [e.g. us-east-1]
• Was the solution modified from the version published on this repository?
• If the answer to the previous question was yes, are the changes available on GitHub?
• Have you checked your service quotas for the sevices this solution uses?
• Were there any errors in the CloudWatch Logs?

Screenshots

Additional context