crossplane v2: namespaced MRs

[sergenyalcin]

Description of your changes

Introduce namespaced MRs for crossplane v2 support.

notable changes:

• New APIs are under tf.m.upbound.io group
• Introduced the cluster-scoped ClusterProviderConfig.tf.m.crossplane.io for new APIs to refer to a cluster-scoped provider config.
• crossplane-runtime is bumped to v2
• spec.providerConfigRef is now accepts kind parameter, ProviderConfig or ClusterProviderConfig for new MRs.
• spec.providerConfigRef now defaults to ClusterProviderConfig with name default when omitted.
• External Secret Store support is removed from MRs (spec.publishConnectionDetailsTo is removed)
• Legacy cluster-scoped MRs are left as is. Provider will serve both new and legacy APIs. Upgrading is backward-compatible.
• Added examples for namespaced MRs.

Note for reviewers

this PR duplicates most of the controller logic and apis for namespaced MRs with several namespace-specific code modified. A refactoring of types and controllers should follow-up.

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable to ensure this PR is ready for review.

How has this code been tested

Tested locally.

[turkenf]

Thank you @sergenyalcin, LGTM