[Not Intended to Merge] Initial POC implementation of OpenTelemetry

[b-yogesh]

This is a test PR that implements the initial POC implementation of OpenTelemetry to get observability insights into the xcube server.

Opentelemetry (OT) is used to extract the traces. In production, it is recommended to use a Collector (a concept from OT) but for this POC, we can directly send the data to the backend (Jaeger in this case).
Jaeger is a docker container (for development purposes) that collects these traces and displays them in an UI

To run Jaeger, just run this

docker run --rm --name jaeger \                             
 -e COLLECTOR_ZIPKIN_HOST_PORT=:9411 \
  -p 6831:6831/udp \
  -p 6832:6832/udp \
  -p 5778:5778 \
  -p 16686:16686 \
  -p 4317:4317 \
  -p 4318:4318 \
  -p 14250:14250 \
  -p 14268:14268 \
  -p 14269:14269 \
  -p 9411:9411 \
  jaegertracing/all-in-one:1.60

Reference links:
OpenTelemetry
Jaeger
Youtube-OT Basics

Checklist:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/source/*
• Changes documented in CHANGES.md
• GitHub CI passes
• AppVeyor CI passes
• Test coverage remains or increases (target 100%)