[RFC] [GGUI] GGUI user experience improvement

[YuCrazing]

To improve the user experience of GGUI, we would like to add some essential utilities according to users' feedback.

All newly add features will be tracked in this issue:

• [x] Support getting camera's view / projection matrix. (https://github.com/taichi-dev/taichi/pull/5345)
• [x] Support fetching scene's image buffer (to CPU). (https://github.com/taichi-dev/taichi/pull/5354)
• [x] Support fetching scene's depth buffer (to CPU). (https://github.com/taichi-dev/taichi/pull/5410)
• [x] Support getching scene's depth buffer (to GPU). (https://github.com/taichi-dev/taichi/pull/5455)
• [x] Support exporting video/gif to files. (https://github.com/taichi-dev/taichi/pull/5354)
• [x] Support rendering a part data of field. (https://github.com/taichi-dev/taichi/pull/5388)
• [x] Support mesh instances' rendering. (https://github.com/taichi-dev/taichi/pull/5546)
• [x] Support 3D lines' rendering. (https://github.com/taichi-dev/taichi/pull/5492, https://github.com/taichi-dev/taichi/pull/5495)
• [ ] Support rendering from ndarray.

Most of our development will be independent of @PENGUINLIONG 's GGUI refactoring plan https://github.com/taichi-dev/taichi/issues/5426, we will take GGUI's refactoring as the highest priority if any conflict happens in the future development.

[Morcki]

On Track of Correctness Tasklist: https://github.com/taichi-dev/taichi/issues/5426#:~:text=%C2%A0%235277%20).-,Correctness,-Ensure%20any%20kernel