Deprecation plan for OTel Python OpenCensus support

[tammy-baylis-swi]

OpenTelemetry Specification 1.58.0 (open-telemetry/opentelemetry-specification#5164) will introduce deprecation of OpenCensus compatibility: open-telemetry/opentelemetry-specification#5138

OTel Python has some open, older OpenCensus issues that will therefore no longer be worth addressing:

• Flaky opencensus shim test #3975
  • PR: fix: clear OpenCensus execution context in TestPatch setUp/tearDown #5262
• OpenCensus metrics bridge #3068
• OpenCensus trace shim #3203

This is still relevant, but part of it is changing OpenCensus code so linking here for reference #4839

For this ticket, come up with a plan for OTel Python to adhere to spec and clean up debt.