feat(csi): restructure the CSI as different mr executable

[lampajr]

Fixes #338

Description

With this PR I am proposing a possible solution to the way CSI is managed here (ref. #338).

Instead of having a separate Go module, I am just proposing to simply create a new executable in a dedicated folder that makes use of model registry source code (as it was previously though)

This should completely remove the issue we were encountaring with false negative on dependabot.

Pro

• Nothing changed wrt the previous approach in terms of deliverable
• A tagged release of model registry contains both source code for MR itself and CSI
• Model registry and CSI container images are in sync in terms of release version and source code
• The CSI does not explicitly pin any version of model registry as it directly uses the model registry source code (as it was before but without any confusion)
• The maintenance is a lot eaiser, just one module for both

Cons

• I had to add kserve dependency in the model registry even if for the model-registry itself is not actually required

How Has This Been Tested?

Updated the existing CI tests

Merge criteria:

• All the commits have been signed-off (To pass the DCO check)

• The commits have meaningful messages; the author will squash them after approval or in case of manual merges will ask to merge with squash.
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has manually tested the changes and verified that the changes work.
• Code changes follow the kubeflow contribution guidelines.

If you have UI changes

• The developer has added tests or explained why testing cannot be added.
• Included any necessary screenshots or gifs if it was a UI change.
• Verify that UI/UX changes conform the UX guidelines for Kubeflow.

[lampajr]

/cc @Al-Pragliola @tarilabs

As discussed in slack, here the final proposal with the suggested changes 🚀

[Al-Pragliola]

/lgtm

I will close #598 in favor of this, thank you for taking care of this issue 🙏

All tests pass locally and on CI, I also checked possible differences in image size and everything works as intended.

MR pre refactoring

MR post refactoring

CSI pre refactoring

CSI post refactoring

[tarilabs]

per discussions in the KF Model Registry biweekly meeting last 2024-12-09, thanks a lot @lampajr for these contributions and thank you @Al-Pragliola for the great help too

/lgtm
/approve

[google-oss-prow]

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