Update Eigen to commit:aa6964bf3a34fd607837dd8123bc42465185c4f8

CHANGELOG
=========
aa6964bf3 - Work around MSVC issue in Block XprType.
877c2d1e9 - fix typo in comment
0c9526912 - Pass div_ceil arguments by value.
d9839718a - [ROCm] Replace HIP_PATH with ROCM_PATH for rocm 6.0
5bdf58b8d - Eliminate use of _res.
a96545777 - Consolidate multiple implementations of divup/div_up/div_ceil.

PiperOrigin-RevId: 575252840
Change-Id: Ief064e2e85f2d17f6267a36093fcdfbd81d37dad
22 files changed