Make annotation based resource tracking the new default

[jannfis]

Summary

Argo CD should switch the default resource tracking method to the new annotation based resource tracking method.

Motivation

Label based resource tracking has proven to be very limited in the past due to the 63 characters limit of a label's value. The recently introduced annotation based resource tracking has significantly improved resource tracking for a couple of important use cases, e.g.

• a controller makes a copy of a managed resource (or, uses such a managed resource as the source of other resources it creates) and in the process copies labels an annotations from the managed resource to the newly created resource
• application tracking needs to consider more than just the application name (apps in any namespace is such an example), and thereby easily exceed the 63 character limit

People used to workaround some of these issue using sync options such as IgnoreExtraneous=true and Prune=false, but this is cumbersome and also not possible in any scenarios.

Proposal

Make annotation based (or even annotation+label) resource tracking the new default. This is a breaking change, therefore it should be changed on a major version bump.

[terrytangyuan]

+1

[terrytangyuan]

I submitted a PR for this for v3.0 to open up some early discussions #18961