[addon-operator] drop hooks and standalone CRDs from nelm render

[Glitchy-Sheep]

Backport of #815 to release-1.21 (DKP 1.76). Clean cherry-pick of ccaf571, no conflicts.

Overview

Fixes the false AbsentHelmResourcesDetected loop:

• modules whose charts have helm hooks got reinstalled every ~5 minutes.
• NelmClient.Render now returns only regular release resources, same as helm3 rs.Manifest.

What this PR does / why we need it

Problem

• Render output feeds two consumers: the release checksum (moduleChecksum) and the absent-resources monitor.
• helm3lib returned rs.Manifest - regular resources only. The nelm client returns every object from chartRenderResult.Resources, including helm hooks and standalone CRDs.
• A pre-delete hook Job exists in the cluster only while the release is being deleted. The monitor saw it "missing" on every tick and fired AbsentHelmResourcesDetected.
• The checksum skip did not help: shouldRunHelmUpgrade runs the absent check on the same list, so every such ModuleRun forced a real upgrade.
• Observed on the virtualization module: 815 release revisions in 3 days with identical values and manifests. With 10 revisions of history, rollback window shrank to ~50 minutes.

Fix

• NelmClient.Render keeps only resources with StoreAs == regular.
• One string comparison on a field nelm already fills - no extra YAML parsing.
• Hooks (StoreAs == hook) and standalone CRDs (StoreAs == none) stay out of the checksum and the monitor list.

Before / After

Before: a chart with a pre-delete hook loops forever: absent event -> forced upgrade -> new revision every ~5 minutes.

After: the monitor tracks only objects that must exist in the cluster; with unchanged values and manifests there are no events, no upgrades, no new revisions.

Special notes for your reviewer

Tests

• Test_NelmClient_Render_KeepsOnlyRegularResources - hooks and standalone CRDs stay out of Render output; two regular resources keep a single --- separator. The test fails without the filter (verified).

Rollout notes

• After rollout, modules with hooks get one legit new revision: moduleChecksum no longer covers hook manifests.
• deckhouse-controller module render no longer prints hooks and standalone CRDs - same as it was with helm3.
• Also bumps nelm to v1.28.0 (comes with the cherry-picked commit; adds the NELM_FEAT_ADOPT_DECKHOUSE_CONTROLLER_FIELDS feature gate, off by default).