sw:vec: Add scalar build support to build rv32im binaries Add CMake option "BUILD_SIMPLIFIED_CORE" to use the macros defined in https://spacebeaker-review.googlesource.com/c/shodan/sw/vec/+/18021 to build rv32im SW binaries. Also remove the unused "riscv_vector.h" header file in the softrvv test code. The header checks the vector extension in the compilation -march flag and fails if v-ext is not used. Instead of guard it with the macro, I remove the unused header. Change-Id: I85c81cf2d63c232dac53ae15826753d3dd117aa8