Add a 4-way Neon implementation for the convertSequences_noRepcodes
function. Remove 'static' keywords from all of its implementations to
be able to add unit tests.
Relative performance to Clang-18 using: `./fullbench -b18 -l5 enwik5`
Neoverse-V2 before after
Clang-18: 100.000% 311.703%
Clang-19: 100.191% 311.714%
Clang-20: 100.181% 311.723%
GCC-13: 107.520% 252.309%
GCC-14: 107.652% 253.158%
GCC-15: 107.674% 253.168%
Cortex-A720 before after
Clang-18: 100.000% 204.512%
Clang-19: 102.825% 204.600%
Clang-20: 102.807% 204.558%
GCC-13: 110.668% 203.594%
GCC-14: 110.684% 203.978%
GCC-15: 102.864% 204.299%
Co-authored by, Thomas Daubney <Thomas.Daubney@arm.com>