Drop support for Jaeger Exporter

[Kielek]

As we are in pre 1.0.0 release, it will be good to remove it.
If someone needs it, there is a possibility to load it by plugin.

See open-telemetry/opentelemetry-specification#2859

[pellared]

1. Jaeger is still very popular
2. Plugins should be used "as last resort", their primary use case is to allow creating distributions. I think that the users shouldn't not use them unless necessary.
3. Let's track the issue in the spec. For sure we should make a decision before 1.0.0.

[RassK]

Doesn't seem as a fat dependency in SDK. Since we also load it if we need it, there is not many issues keeping it until deprecation notice is official.

Plugins should be used "as last resort", their primary use case is to allow creating distributions. I think that the users shouldn't not use them unless necessary.

Especially true without integration layer. Having integration through magic methods could cause loads of issues. At least distributors know more what's going on.

[pellared]

Deprecation note is official open-telemetry/opentelemetry-specification#2858

I think we are good to remove it. Removing the "milestone" to discuss if we want to make it sooner.