Define support guidelines for major revisions

[atoulme]

As we gear towards supporting v1, we will need to define a set of support statements providing answers to the following:

• When we publish a v2, do we still support v1?
• If yes, how long do we plan to support v1 once v2 is published?
• Once we release v1, can we make clear that no further releases of v0.x components will be made?

[luke6Lh43]

That is a really good idea!

I think we should have well defined release cycle and support policy. We could follow the one which is used currently in Kubernetes N-2 (meaning that the 3 most recent minor versions receive security and bug fixes), versions more than 2 behind the latest (N-3) are first deprecated and then unsupported. This should be documented and published on opentelemetry.io, so everyone is aware of that.

Also, we should keep figuring out some fancy names for major releases as we have in Kubernetes :)

[mx-psi]

@atoulme Do you feel like #11001 covers all the points on this issue?