Do not report success before package deployment is ready

[turkenh]

Description of your changes

The post establish hook reporting success early before the provider/function deployment has an Available condition resulting the fluctuation in the health of the provider as follows:

❯ kubectl get providers.pkg.crossplane.io -w
NAME            INSTALLED   HEALTHY   PACKAGE                                                    AGE
provider-helm                         xpkg.upbound.io/crossplane-contrib/provider-helm:v0.15.0   0s
provider-helm   True        Unknown   xpkg.upbound.io/crossplane-contrib/provider-helm:v0.15.0   1s
provider-helm   True        True      xpkg.upbound.io/crossplane-contrib/provider-helm:v0.15.0   21s # <--- 
provider-helm   True        False     xpkg.upbound.io/crossplane-contrib/provider-helm:v0.15.0   22s # <--- 
provider-helm   True        True      xpkg.upbound.io/crossplane-contrib/provider-helm:v0.15.0   27s

Note that it reports unhealthy after reporting healthy.

This PR fixes this situation by properly handling Deployment not having the available status at all. Now it becomes as follow:

❯ kubectl get providers.pkg.crossplane.io -w
NAME            INSTALLED   HEALTHY   PACKAGE                                                    AGE
provider-helm                         xpkg.upbound.io/crossplane-contrib/provider-helm:v0.15.0   0s
provider-helm   True        Unknown   xpkg.upbound.io/crossplane-contrib/provider-helm:v0.15.0   1s
provider-helm   True        False     xpkg.upbound.io/crossplane-contrib/provider-helm:v0.15.0   22s
provider-helm   True        False     xpkg.upbound.io/crossplane-contrib/provider-helm:v0.15.0   22s
provider-helm   True        True      xpkg.upbound.io/crossplane-contrib/provider-helm:v0.15.0   29s

I have:

• Read and followed Crossplane's contribution process.
• Added or updated unit and E2E tests for my change.
• Run make reviewable to ensure this PR is ready for review.
• Added backport release-x.y labels to auto-backport this PR, if necessary.
• Opened a PR updating the docs, if necessary.