bugfix: OpenTracing Shim not converting exceptions to format expected by OpenTelemetry

[zhihali]

Description

Fixes #4152 Add a sanitize function to make sure the attribute value is converted to string, which align with attributes definition. Add the warning at logs to better track the error, make sure it will not be ignored after sanitized.

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

tox -e lint-opentelemetry-opentracing-shim

Does This PR Require a Contrib Repo Change?

• [ ] Yes. - Link to PR:
• [x] No.

Checklist:

• [x] Followed the style guidelines of this project
• [x] Changelogs have been updated
• [x] Unit tests have been added
• [ ] Documentation has been updated