[Don't Merge] Draft Performance Overhead on rv64im CKB-VM

[XuJiandong]

This test estimates the performance overhead of the CKB-VM RV64IM implementation running on QEMU.

• Raw CKB-VM Instructions: Instructions executed by CKB-VM on the native machine
• QEMU Instructions: Instructions executed by CKB-VM running on the QEMU emulator (riscv64, rv64im)
• Emulation Overhead: The ratio of QEMU / Native, representing the emulation cost when running on QEMU

Result via bash rv64im-benchmark.sh:

Test	Raw CKB-VM Instructions	QEMU Instructions	Emulation Overhead
ed25519	0.99 M	321.5 M	325x
k256_ecdsa	3.95 M	1258.2 M	319x
k256_schnorr	1.89 M	688.0 M	364x
p256	4.00 M	797.1 M	199x
rsa	3.55 M	811.2 M	229x
secp256k1_ecdsa	0.53 M	193.5 M	365x
secp256k1_schnorr	0.52 M	188.5 M	362x
sphincsplus_ref	33.84 M	7107.3 M	210x

[XuJiandong]

Already have dedicated repo for benchmark: https://github.com/XuJiandong/ckb-vm-on-sp1