Add sign and signature verification tool

What's Changed

• add sign tool by @shrimalmadhur in #386
• Add signature verification tool in rosetta-cli by @shrimalmadhur in #387
• add key generate command by @shrimalmadhur in #388
• update rosetta-skd-go to 0.8.3 by @jingweicb in #389

Full Changelog: v0.10.2...v0.10.3