Envoy: api: move configuration of tracer provider implementations out of `config.trace` into `extensions.tracers.<provider>`

[yskopets]

Title: move configuration of tracer provider implementations out of config.trace into extensions.tracers.<provider>

Context:

• proper placement of extension-specific configuration would have prevented #10576

[mattklein123]

cc @sanjaypujare can you potentially do this as part of solving the OpenCencus issue? It should be straightforward.

[sanjaypujare]

See my comment in https://github.com/envoyproxy/envoy/issues/10576#issuecomment-612179006 . I can get it to it later but not now.

[yskopets]

@sanjaypujare @mattklein123 I will take a look into it.

[yskopets]

@mattklein123

Just to clarify, what do you think should be in the scope of this task ?

E.g.,

• I could just add udpa.annotations.file_migrate to provider-specific message types and they will be moved into extensions.tracers.<provider> in v4alpha
• or, do you expect these types to be moved into extensions.tracers.<provider> already in v3 ? I think, it's doable, but it requires more automation from api/tools to keep config.trace.v3 and extensions.tracers.<provider>.v3 in sync, so that users could configure Envoy with any of these types

WDYT ?

[mattklein123]

@yskopets I think just doing this for v4alpha is fine but I will defer to @htuch on the best plan forward. Thank you!

[htuch]

Yeah, I think this is best done in v4alpha to avoid breaking API changes, thanks.