fix(libzkp): try to convert to string for panic errors

[silathdiir]

Purpose or design rationale of this PR

Reference this panic-handling code of zkevm-circuits testool, fix to the similar logic in libzkp (to avoid returning error as Any {...}).

Suppose to test again and release in next version.

PR title

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• build: Changes that affect the build system or external dependencies (example scopes: yarn, eslint, typescript)
• ci: Changes to our CI configuration files and scripts (example scopes: vercel, github, cypress)
• docs: Documentation-only changes
• feat: A new feature
• fix: A bug fix
• perf: A code change that improves performance
• refactor: A code change that doesn't fix a bug, or add a feature, or improves performance
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
• test: Adding missing tests or correcting existing tests

Deployment tag versioning

Has tag in common/version.go been updated or have you added bump-version label to this PR?

• No, this PR doesn't involve a new deployment, git tag, docker image tag
• Yes

Breaking change label

Does this PR have the breaking-change label?

• No, this PR is not a breaking change
• Yes

[codecov]

Codecov Report

Merging #949 (f872f56) into develop (5eed174) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #949   +/-   ##
========================================
  Coverage    50.29%   50.29%           
========================================
  Files           96       96           
  Lines        10001    10001           
========================================
  Hits          5030     5030           
  Misses        4557     4557           
  Partials       414      414           

Flag	Coverage Δ
common	54.56% <ø> (ø)
coordinator	18.80% <ø> (ø)
database	42.85% <ø> (ø)
rollup	66.35% <ø> (ø)

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