Fix FileNotFoundException handling in segment download API

[rsrkpatwari1234]

Fixes #16231

Problem

When the /segments controller API hit a FileNotFoundException (or HTTP 404), it showed these issues:

1. Unnecessary retries: The segment fetcher retried up to 3 times even when the file did not exist, wasting time and resources.
2. Wrong HTTP status: The API returned HTTP 500 (Internal Server Error) instead of HTTP 404 (Not Found).
3. Obscured root cause: The original FileNotFoundException was wrapped in AttemptsExceededException, making debugging harder.

Solution

In this PR, I have implemented two improvements -

1. Skip retries for FileNotFoundException: In BaseSegmentFetcher and HttpSegmentFetcher, we detect FileNotFoundException (and, for HTTP, HttpErrorStatusException with status 404) in the exception cause chain and rethrow immediately so no retries are performed.
2. Return HTTP 404: In PinotSegmentUploadDownloadRestletResource, we catch these cases (via ExceptionUtils.isCauseInstanceOf and getFirstCauseOfType) and return Response.Status.NOT_FOUND (404) instead of 500.

Unit Tests
✅ 4 new tests added to verify FileNotFoundException behaviour
✅ All existing tests pass - no breaking changes

bugfix

[rsrkpatwari1234]

@Jackie-Jiang @ankitsultana Requesting your help in running the above workflow and reviewing the changes

[Jackie-Jiang]

Please fix the test failure

[codecov-commenter]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
20700	1	20699	59

View the full list of 1 ❄️ flaky test(s)

org.apache.pinot.core.data.manager.BaseTableDataManagerTest::testAddNewSegmentUseLocalCopy

Flake rate in main: 89.80% (Passed 10 times, Failed 88 times)

Stack Traces | 1.35s run time

expected [Operation failed after 3 attempts] but found [org.apache.pinot.spi.filesystem.LocalPinotFS$LocalPinotFSException: java.io.FileNotFoundException: Source '' does not exist]

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[rsrkpatwari1234]

@Jackie-Jiang Requesting your review. The test failure seems unrelated to my change

[Jackie-Jiang]

I think it is related:

[ERROR]   BaseTableDataManagerTest.testAddNewSegmentUseLocalCopy:585 expected [Operation failed after 3 attempts] but found [org.apache.pinot.spi.filesystem.LocalPinotFS$LocalPinotFSException: java.io.FileNotFoundException: Source '' does not exist]