Add Rust benchmarks for base64, sha512 and regex matching

[Lubrsi]

Initial results on my MacBook Pro M4 14 core machine:

Suite          Test                    Mean ± σ        Range (min … max)
-------------  ----------------------  --------------  -------------------
WasmRustBench  base64-bench.wasm       24.488 ± 0.513  24.030 … 25.320
WasmRustBench  regex-match-bench.wasm  4.632 ± 0.030   4.600 … 4.660
WasmRustBench  sha512-bench.wasm       37.930 ± 0.199  37.650 … 38.100