Remove unused LhsPacketType typedef in gebp_peeled_loop

Summary

LhsPacketType was computed from LhsArray at the function level in gebp_peeled_loop::run() but only used inside EIGEN_GEBP_ARM64_3P_WORKAROUND and EIGEN_GEBP_SSE_SPILLING_WORKAROUND macros. When both macros expand to nothing (e.g. Clang 20/21 on x64), this triggers -Wunused-local-typedef, which becomes an error with -Werror.

Fix: move the type computation (remove_all_extents_t<remove_reference_t<LhsArray>>) directly into each macro, passing LhsArray instead of the pre-computed LhsPacketType.

Fixes #3029 (closed)

Test plan

• product_small, product_extra, basicstuff, nomalloc all pass (50/50)
• No unused typedef warnings with clang++ -std=c++20 -Wunused-local-typedef