[DOC]: Improve reference example code snippets in Thrust

[gonidelis]

Thrust code snippets under the reference page of our algorithms are poor in two way.

1. Although we need to keep the concise we also need to make them more complete. Per the cppreference style of examples, we need clear distinction between input and output in the text. Encourage the use of thrust::device_vector instead of custom allocated arrays. Showcase both generic cases and edge cases.

2. Extract them to literalincludes to make sure they are full compilable scripts that can be cut pasted into main(). It's very discouraging for a new user when that's not the case. This should also resolve:

• [DOC]: thrust::partition_copy docs are wrong #2792
• [DOC]: thrust::stable_sort docs are wrong #2747
• [DOC]: copy_n docs formatting bug #2748.