### What changes were proposed in this pull request?
Some minor performance optimizations in the internal implementation
### Why are the changes needed?
During our use of Flink with Celeborn, we identified several minor optimizations that can be made:
1. In the client side, the Flink-Celeborn client parses the `pushDataTimeout` configuration too frequently, which is unnecessary and cpu-intensive.
2. On the worker side, Celeborn needs to filter readers that are able for reading. However, using Java Stream's collection operations is costly in terms of performance.
3. Also on the worker side, Celeborn currently checks whether a reader can continue reading by comparing the current read offset with the total file size. This check involves retrieving the total file size, which is an expensive operation. Since this value is constant, it should be cached in memory instead of being fetched multiple times.
4. In the Flink’s hybrid shuffle integration, the `EndOfSegment` event should not be bundled with data buffers. If it is, there is a risk of data corruption or misinterpretation.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
Manual test.
Closes#3318 from codenohup/CELEBORN-2029.
Authored-by: codenohup <huangxu.walker@gmail.com>
Signed-off-by: SteNicholas <programgeek@163.com>
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