Update changelog for next release

[cijothomas]

1.3.0.beta.1 for Core
(A bit odd for Prometheus which goes 1.2.0-rc5 to 1.3.0-beta. After the initial stable release, we expect Prometheus to be versioned release together with the core packages)
1.0.0-rc9.3 for others.

[reyang]

LGTM.

[reyang]

I'm kind of battling with myself.

Do we think we can/should do the same for Instrumentation Libraries? (e.g. OpenTelemetry.Instrumentation.Http). In other words, let's say if OpenTelemetry.Instrumentation.Http is Stable today, do we release it as 1.0.0 or 1.2.0? (I feel it should be 1.2.0)

Also it seems a bit weird to have the following release sequence:

• 1.2.0-rc1
• 1.2.0-rc2
• 1.2.0-rc3
• 1.2.0-rc4
• 1.2.0-rc5
• BOOM there is no 1.2.0 Stable because we're waiting for the spec
• 1.3.0-alpha.1

[alanwest]

I think what we need to decide in the long run is what our versioning scheme should communicate to end users. Looks like you started this discussion with #917. I'll add some thoughts on that issue to continue the conversation.

Even though it's odd, I think it's ok for now that Prometheus will jump past a 1.2.0 stable release.

if OpenTelemetry.Instrumentation.Http is Stable today, do we release it as 1.0.0 or 1.2.0? (I feel it should be 1.2.0)

I also agree that it should be 1.x.0 where x = current core stable version at the time instrumentation goes stable. Again, while odd, I think it'll be ok to be odd up to the point where we've gotten a stable release out of all components.