add option to disable generation contrib ops (#27369)
### Description
This pull request introduces a new build option to selectively disable
generation-related contrib operators (such as BeamSearch,
WhisperBeamSearch, GreedySearch, and Sampling) in ONNX Runtime.
The implementation of those operators contributes non-trivial binary
size to the final artifact. This offers a way to reduce the binary size
in some use scenarios.
