feat(stackable-versioned): Generate downgrade From impls

[Techassi]

This PR adds support to downgrade CRDs.

• The #[versioned()] macro generates From impls for downgrading.
• Change the convert_with parameter of the changed() action accordingly to support customizing both the upgrade and downgrade conversion function. There are now two separate parameters: upgrade_with and downgrade_with.
• Emit a status subresource to be able to track values of the resource during upgrade and downgrade operations.

[sbernauer]

Thanks for addressing my points, another round of review :)

[sbernauer]

LGTM, but there is still one leftover:

diff --git a/crates/stackable-versioned-macros/tests/trybuild.rs b/crates/stackable-versioned-macros/tests/trybuild.rs
index 891cc60..d58c32d 100644
--- a/crates/stackable-versioned-macros/tests/trybuild.rs
+++ b/crates/stackable-versioned-macros/tests/trybuild.rs
@@ -21,9 +21,9 @@ mod inputs {
             // mod attribute_enum;
             // mod attribute_struct;
             // mod basic_struct;
-            // mod convert_with;
             // mod deprecate_enum;
             // mod deprecate_struct;
+            // mod downgrade_with;
             // mod enum_data_simple;
             // mod generics_defaults;
             // mod generics_module;