Flatten hudi_trino_ci.yml the way bot.yml was flattened in #19890

Part of #19524.

`hudi_trino_ci.yml` still uses a `changes` job that every other job `needs`. On the shared ASF runner pool that is a second trip through the queue for every run, which #19890 measured at 1 to 3 minutes when the pool is quiet and 20 to 270 minutes when it is busy. #19890 removed the same pattern from bot.yml by moving the skip to a trigger-level `paths` filter.

The comment above the Trino workflow's trigger also now contradicts bot.yml: it says a path-filtered workflow leaves an expected run "permanently pending". That is only true for required status checks, and `test-hudi-trino-plugin` is no longer required (the contexts list was reset in #19523).

Proposed change: move the Trino path list to a trigger-level `paths` filter, drop the `changes` job and its `needs`, and soften the comment to say pending applies only to required contexts.

Start by comparing hudi_trino_ci.yml with the flattened bot.yml change from #19890, focusing on the trigger comment, path list, changes job, and jobs that need it. Done means the path filter is at the trigger level, the changes job and its needs are removed, and the comment limits pending status to required contexts.

Written by the indexing model from the issue text.