feat(v3alpha): write actions (#8225)

# Which Problems Are Solved

The current v3alpha actions APIs don't exactly adhere to the [new
resources API
design](https://zitadel.com/docs/apis/v3#standard-resources).

# How the Problems Are Solved

- **Breaking**: The current v3alpha actions APIs are removed. This is
breaking.
- **Resource Namespace**: New v3alpha actions APIs for targets and
executions are added under the namespace /resources.
- **Feature Flag**: New v3alpha actions APIs still have to be activated
using the actions feature flag
- **Reduced Executions Overhead**: Executions are managed similar to
settings according to the new API design: an empty list of targets
basically makes an execution a Noop. So a single method, SetExecution is
enough to cover all use cases. Noop executions are not returned in
future search requests.
- **Compatibility**: The executions created with previous v3alpha APIs
are still available to be managed with the new executions API.

# Additional Changes

- Removed integration tests which test executions but rely on readable
targets. They are added again with #8169

# Additional Context

Closes #8168

docs/docusaurus.config.js

@@ -333,7 +333,7 @@ module.exports = {
             },
           },
           action_v3: {
-            specPath: ".artifacts/openapi/zitadel/action/v3alpha/action_service.swagger.json",
+            specPath: ".artifacts/openapi/zitadel/resources/action/v3alpha/action_service.swagger.json",
             outputDir: "docs/apis/resources/action_service_v3",
             sidebarOptions: {
                 groupPathsBy: "tag",