Deprecate opentracing shim public API

[ADITYA-CODE-SOURCE]

Deprecate the public opentracing-shim entrypoints and update the module documentation in line with the OpenTelemetry specification guidance on OpenTracing compatibility.

This keeps behavior unchanged and limits the scope to deprecation annotations and docs for the legacy shim surface.

Fixes #8323

[otelbot]

⚠️ API changes detected — additional maintainer review required

@jack-berg @jkwatson

This PR modifies the public API surface area of the following module(s):

• opentelemetry-opentracing-shim

Please review the changes in docs/apidiffs/current_vs_latest/ carefully before approving.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.85%. Comparing base (af4dff2) to head (ca52264).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8373   +/-   ##
=========================================
  Coverage     90.85%   90.85%           
  Complexity     7954     7954           
=========================================
  Files           896      896           
  Lines         24010    24010           
  Branches       2390     2390           
=========================================
  Hits          21815    21815           
  Misses         1457     1457           
  Partials        738      738           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.