CanMV-K230 (Kendryte K230, C908) ascii to utf32 benchmark
Implements a void ascii_to_utf32(uint32_t *restrict dest, uint8_t const *restrict src, size_t len) function, which convers a ASCII string to utf32 string. This is basically just zero extending from 1 to 4 bytes.
- rvv_ext: zero extends to higher LMUL and stores directly
- rvv_vsseg: uses segment store
- rvv_vss: writes zero, then fills in lower bits with strided store