feat: allow "duplicate" kinds in the config patches

[smira]

This applies to a single multi-document config patch.

Allow the patch documents to have duplicates across kinds/names. The config patch code was re-using the path for machine configuration loading, so allow to load skipping all validations - the patches can be pretty much relaxed compared to real machine config.

Adjust patch interface to leave less assumptions on what can be done - we can either iterate over patch documents, or convert patch back to bytes.

[Copilot]

Pull request overview

This PR relaxes config patch loading to allow duplicate documents (same apiVersion/kind/name) within a single multi-document patch, and adjusts the strategic patch interface to avoid exposing assumptions about typed provider access.

Changes:

• Add an “unvalidated” readonly container + a WithNoValidation() configloader option to bypass duplicate/conflict validation for patch inputs.
• Allow duplicates in the YAML decoder path when validation is disabled.
• Update the strategic patch interface from Provider() to Bytes() and add tests covering mixed/duplicate patch documents.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pkg/machinery/config/container/container.go	Adds NewReadonlyUnvalidated for relaxed patch-loading containers.
pkg/machinery/config/configpatcher/strategic.go	Adjusts StrategicMergePatch interface and strategic merge behavior for appended docs.
pkg/machinery/config/configpatcher/load.go	Loads strategic patches with WithNoValidation() to allow duplicates.
pkg/machinery/config/configpatcher/load_test.go	Updates strategic patch assertions to use Documents()/Bytes() instead of typed provider access.
pkg/machinery/config/configpatcher/apply_test.go	Adds coverage for applying mixed patches (including duplicates) via both WithConfig and WithBytes.
pkg/machinery/config/configpatcher/testdata/patchmixed/base.yaml	New base config fixture for mixed patch test.
pkg/machinery/config/configpatcher/testdata/patchmixed/patch.yaml	New patch fixture containing duplicates for the same kind/name.
pkg/machinery/config/configpatcher/testdata/patchmixed/expected.yaml	New expected output fixture for mixed patch test.
pkg/machinery/config/configloader/internal/decoder/decoder.go	Adds allowDuplicates to decoding to permit duplicates when validation is disabled.
pkg/machinery/config/configloader/internal/decoder/decoder_test.go	Extends decoder tests to cover “allow duplicates” mode.
pkg/machinery/config/configloader/configloader.go	Threads noValidation through decoding and returns an unvalidated container when set.
pkg/machinery/config/configdiff/mergepatch_test.go	Updates tests to use the new StrategicMergePatch.Bytes() method.

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