feat: reflection server

[rustatian]

Reason for This PR

closes: roadrunner-server/roadrunner#1208

Description of Changes

• New boolean configuration key enable_reflection_server to activate reflection server
• https://github.com/grpc/grpc-go/blob/master/Documentation/server-reflection-tutorial.md
• https://github.com/grpc/grpc/blob/master/doc/command_line_tool.md
• https://github.com/fullstorydev/grpcui

License Acceptance

By submitting this pull request, I confirm that my contribution is made under
the terms of the MIT license.

PR Checklist

[Author TODO: Meet these criteria.]
[Reviewer TODO: Verify that these criteria are met. Request changes if not]

• All commits in this PR are signed (git commit -s).
• The reason for this PR is clearly provided (issue no. or explanation).
• The description of changes is clear and encompassing.
• Any required documentation changes (code and docs) are included in this PR.
• Any user-facing changes are mentioned in CHANGELOG.md.
• All added/changed functionality is tested.