Update Eigen to: https://gitlab.com/libeigen/eigen/-/commit/3d9051ea84a5089b277c88dac456b3b1576bfa7f

BEGIN_PUBLIC

Update Eigen to: https://gitlab.com/libeigen/eigen/-/commit/3d9051ea84a5089b277c88dac456b3b1576bfa7f

Additional minor changes to account for API change in `TensorDeviceGpu` - static variables replaced
by a safer singleton class.

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For TFRT, the OSS eigen version hasn't been updated in over a year.  This is now corrected, and
required a small change in handling `__shfl_down_sync` for `Eigen::half`, for which an overload
is now provided.

PiperOrigin-RevId: 374792818
36 files changed