Validate Whisper timestamp token bounds (#33824)
This pull request strengthens input validation for Whisper model token
IDs and improves test coverage for these checks. The main focus is on
ensuring that special token IDs (such as EOS and timestamp tokens) are
within valid vocabulary bounds, preventing out-of-range errors during
generation. Additionally, new unit tests are added to verify these
validations.
**Validation Improvements:**
* Added explicit checks in
`BeamSearchParameters::ValidateWhisperTimestampTokenId` and
`TimestampLogitsProcessor::Process` to ensure that `eos_token_id`,
`end_of_text_token_id`, and timestamp token IDs are within the valid
vocabulary range, throwing informative errors if not.
[[1]](diffhunk://#diff-5849847bc23361fe9582a0dad2a33e947961eba317a90bb0b1125f3cdecc49b4R165-R167)
[[2]](diffhunk://#diff-4c14c3eea859e0355f15377e8db7e7178ae6d4ae38bf04f2611e7910b3719146R185-R200)
**Test Enhancements:**
* Introduced new unit tests in `beam_search_test.cc` to verify that
invalid token IDs are correctly rejected and valid boundary values are
accepted, including tests for out-of-range EOS and timestamp token IDs.
* Added a `TestSequences` helper class and `MakeTimestampProcessor`
factory function to facilitate testing of the logits processor.
* Included necessary headers for new tests and processor usage.
[[1]](diffhunk://#diff-782b3e352d8957cd1226d1b87f2127c58efd5ba7a6472528afbdd6baa8232198R4)
[[2]](diffhunk://#diff-782b3e352d8957cd1226d1b87f2127c58efd5ba7a6472528afbdd6baa8232198R19)
