SNOW-1706990 Convert test_manager.py to use v2 entities (#1722)

Updates tests in `test_manager.py` to use a v2 test project and call out to the v2 entities directly instead of going through the `NativeAppManager`. I've kept the diff as simple as possible and avoided introducing too many helpers or reorganizing the code, that can be done separately if necessary (the top priority is to just work towards removing `NativeAppManager` and all these static methods first).

src/snowflake/cli/_plugins/nativeapp/entities/application_package.py

@@ -232,7 +232,13 @@ def action_drop(self, action_ctx: ActionContext, force_drop: bool, *args, **kwar
  )
 
  def action_validate(
- self, action_ctx: ActionContext, interactive: bool, force: bool, *args, **kwargs
+ self,
+ action_ctx: ActionContext,
+ interactive: bool,
+ force: bool,
+ use_scratch_stage: bool = True,
+ *args,
+ **kwargs,
  ):
  model = self._entity_model
  workspace_ctx = self._workspace_ctx
@@ -266,7 +272,7 @@ def action_validate(
  post_deploy_hooks=model.meta and model.meta.post_deploy,
  package_scripts=[], # Package scripts are not supported in PDFv2
  policy=policy,
- use_scratch_stage=True,
+ use_scratch_stage=use_scratch_stage,
  scratch_stage_fqn=f"{package_name}.{model.scratch_stage}",
  )
  workspace_ctx.console.message("Setup script is valid")