Add reverse propagation of telemetry tags

[Arnab Nandy (arnabnandy7)]

Issue describing the changes in this PR

resolves #867

This change adds support for reverse propagation of request telemetry tags from the Java worker to the Functions host.

• Updates the language worker protobuf to v1.12.0-protofile.
• Provides invocation trace attributes to function code through the existing TraceContext.getAttributes() API.
• Adds the final trace attributes to InvocationResponse.trace_context_attributes.
• Allows the host to attach custom attributes to the corresponding request telemetry.

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• I have added all required tests (Unit tests, E2E tests)

Additional information

A functional test verifies that attributes added through ExecutionContext.getTraceContext().getAttributes() are included in the invocation response sent back to the Functions host.

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