Colorful NVTX ranges for the task and GPU ownership

[jihoonson]

#11596 adds a new NVTX range to track which task owns the GPU during query processing. Currently, the colors of the task range and the GPU ownership are fixed to NvtxColor.DARK_GREEN and NvtxColor.ORANGE, respectively. Using the same color across different tasks is not only not the best choice aesthetically, but, since the GPU ownership changes frequently during the task lifetime, it also makes it hard to have the 10,000-foot view of the GPU ownership changes. It is also hard to match the task range and its associated semaphore ranges. As such, it was suggested in #11596 (comment) to use different colors for each task range, and use the same color for its associated semaphore ranges. Using different colors for different tasks would make the semaphore range more useful.