chore(core): update build as submodule

[universal-itengineer]

Description

Update the CSE build configuration and clean up werf templates related to image/package imports and proxies.

Why do we need it, and what problem does it solve?

The current build configuration contains duplicated and inconsistent logic for package imports, package proxies, and source repository handling. This makes the CSE build flow harder to maintain and increases the risk of errors in image digest generation and package resolution.

This PR simplifies and aligns the werf configuration by:

• unifying source repository usage around SOURCE_REPO
• improving package proxy templates for supported distros
• simplifying package image imports
• switching images-digests generation to use prebuilt jq
• cleaning up outdated template comments and helper definitions

As a result, the build configuration becomes more predictable and easier to maintain.

What is the expected result?

1. Run the module/image build with the updated werf configuration.
2. Verify that package imports are resolved correctly for the affected images.
3. Verify that distro package proxy configuration is applied correctly.
4. Verify that images-digests is generated successfully during the build.
5. Confirm that the updated CSE build flow works without regressions.

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.

Changelog entries

section: core
type: chore
summary: Update CSE build configuration and simplify werf package/image build templates.
impact_level: low