docs: updating changelogs for 0.6 release

[toumorokoshi]

This includes the full changelog for the 0.6 release.

Proposed release text:

Beta v6 release

Documentation

Documentation continues to see large improvements, including re-organizing the examples to make them more discoverable.

Readmes and the getting started guide also have some corrections.

opentelemetry-api

• Add support for lazy events and links (Add support for lazy events and links #474)
• Metrics API no longer uses LabelSet (metrics: Remove LabelSet #527)
• Adding is_remote flag to SpanContext, indicating when a span is remote (Add indicator if SpanContext was propagated from remote parent #516)
• Allow digit as first char in vendor specific trace state key (Allow digit as first chr in vendor specific trace state key #511)

opentelemetry-sdk

• Add support for lazy events and links (Add support for lazy events and links #474)
• Metrics API no longer uses LabelSet (metrics: Remove LabelSet #527)
• Adding is_remote flag to SpanContext, indicating when a span is remote (Add indicator if SpanContext was propagated from remote parent #516)
• Adding a solution to release metric handles and observers (Metrics: add possibility to release handles and observer instruments #435)

opentelemetry-ext-flask

• Add an entry_point to be usable in auto-instrumentation (Add an autoinstrumentation mechanism and an instrumentor for Flask #327)

opentelemetry-ext-jaeger

• Exporting to collector now works (ext/jaeger: fix exporting to collector #508)

[codeboten]

Looks like some duplicate changelog for the API

[codeboten]

LGTM!

[c24t]

LGTM, but I'd love to get a first release of opentelemetry-ext-grpc included here once #476 is merged.