Update Eigen to commit:e8515f78ac098329ab9f8cab21c87caede090a3f

CHANGELOG
=========
e8515f78a - Fix sparse triangular view iterator
6d829e766 - Fix extra semicolon in XprHelper
ba47341a1 - [SYCL-2020] Enabling half precision support for SYCL.
92a77a596 - Fix call to static functions from device by adding EIGEN_DEVICE_FUNC attribute to run methods
8f858a4ea - Export ThreadPool symbols from legacy header.
4e598ad25 - New panel modes for GEMM MMA (real & complex).
2c64a655f - Stage will not be ok if pardiso returned error

PiperOrigin-RevId: 571952024
Change-Id: Ic4ba7448c04e842e42dfb20a19f7cc146a00f66f
34 files changed