Migrate to opentelemetry

[zetaab]

What does this PR do?

Migrates from opentracing to opentelemetry

fixes #9762
fixes #10210
fixes #10235

More

• Added/updated tests
• Added/updated documentation

Additional Notes

only opentelemetry is verified. I do not have datadog/elastic/instana/zipkin setup, so I cannot verify these. Also integration tests are interesting, not sure either is everything there that should be.

tl;dr changes:

datadog

• removed prioritySampling setting. It is not supported anymore in opentelemetry(?)

elastic

• added globalTags and sampleRate settings

haystack

• removed support for haystack.

two reasons for that

1. it was using github.com/ExpediaDotCom/haystack-client-go which is last time updated 4-5 years ago. There is no sense to maintain provider that have library that are not maintained. It can cause security issues to Traefik itself.
2. there is no opentelemetry library for haystack

instana

• removed localAgentHost setting
• removed localAgentPort setting
• removed logLevel setting
• removed enableAutoProfile setting
• added globalTags and sampleRate settings

people need to use standard env variables INSTANA_ENDPOINT_URL & INSTANA_AGENT_KEY to configure instana.

jaeger

• removed support for jaeger, as their documentation states please us opentelemetry instead.

opentelemetry

• added globalTags and sampleRate settings

zipkin

• removed sameSpan setting
• removed id128Bit setting
• added globalTags setting

[zetaab]

this also fixes #10210 it adds user-agent information as attribute

[rtribotte]

Thanks!