add: level, trace.id, span.id attr

[Romira915]

• prometheus: Ignore unknown instrument units (prometheus: Ignore unknown instrument units open-telemetry/opentelemetry-rust#1348)
• Fix metric export data for unused gauges (Fix metric export data for unused gauges open-telemetry/opentelemetry-rust#1363)
• Return consistent Meter for a given MeterProvider (Return consistent Meter for a given MeterProvider open-telemetry/opentelemetry-rust#1351)
• Fix delta aggregation metric reuse (Fix delta aggregation metric reuse open-telemetry/opentelemetry-rust#1434)
• Fix max_scale validation of exponential histogram configuration (Fix max_scale validation of exponential histogram configuration open-telemetry/opentelemetry-rust#1452)
• Prepare for v0.21.2 release (Prepare for v0.21.2 release open-telemetry/opentelemetry-rust#1463)
• add: level, trace.id, span.id attr

Fixes #
Design discussion issue (if applicable) #

Changes

Please provide a brief description of the changes here.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)