fix: update Hyperdisk attach limits to match GCP documentation for Ge…

[arsiesys]

What type of PR is this?

/kind bug

What this PR does / why we need it:
This PR updates the Hyperdisk balanced attach limits to align with the latest GCP documentation for Gen4 machine families (C4, C4D, N4, and C4A).
Previously, a single generic map was used, which did not reflect the correct per-family attach limits for newer machine types.

Key changes:

• Adds separate Hyperdisk attach limit maps for C4, C4D, N4, and C4A machines.
• Updates the attach limit calculation logic to use the appropriate map based on the machine type prefix.
• Updates unit tests to cover new machine type mappings and verify correct limits.

This fixes inaccurate attach limits for Gen4 machines, ensuring compliance with the [official GCP guidance](https://cloud.google.com/compute/docs/general-purpose-machines).

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

• Please verify the machine type prefixes and limit values match the official GCP tables.

fix: Updated Hyperdisk balanced attach limits for C4, C4D, N4, and C4A machine families to match current GCP documentation.

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @arsiesys. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[sunnylovestiramisu]

/ok-to-test

[sunnylovestiramisu]

Do not think we should return 0 here, maybe use the default volumeLimitSmall.

[arsiesys]

I can return a static 15 as the constant is declared in node.go.
Or, I could move the constant from node.go to the common package, let me know which path we prefer.

[sunnylovestiramisu]

/test pull-gcp-compute-persistent-disk-csi-driver-e2e-windows-2022

[sunnylovestiramisu]

/assgn @mattcary

[sunnylovestiramisu]

Why moved this outside? Because if it is inside the machineType is x4 or a4 it does not need to go through the loop. But on the other hand it does not matter so much in the real world

[arsiesys]

You're right! Moving these checks outside was what I though could be a performance optimisation.

Since x4/a4 machine types don't match any of the gen4 prefixes (c4a-, c4-, n4-, c4d-), keeping them inside the loop means we'd unnecessarily check them 4 times (once per iteration) before ultimately returning the correct limit.

By moving them outside:

• gen4 machines: Exit early when matched, never reaching these checks
• Other machines: Only check x4/a4 once at the end

This reduces string comparisons from up to 12 (4 iterations × 3 checks) to at most 6 (4 gen4 + x4 + a4).

I also considered that x4 and a4 may be less frequently used than the ones in the loop. I will put it back if you think it would be better or not the subject of the current PR (would be understandable).

[sunnylovestiramisu]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: arsiesys, sunnylovestiramisu

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[sunnylovestiramisu]

/cherry-pick release-1.20

[k8s-infra-cherrypick-robot]

@sunnylovestiramisu: #2127 failed to apply on top of branch "release-1.20":

Applying: fix: update Hyperdisk attach limits to match GCP documentation for Gen4 machines
Using index info to reconstruct a base tree...
M	pkg/gce-pd-csi-driver/node.go
M	pkg/gce-pd-csi-driver/node_test.go
Falling back to patching base and 3-way merge...
Auto-merging pkg/gce-pd-csi-driver/node_test.go
CONFLICT (content): Merge conflict in pkg/gce-pd-csi-driver/node_test.go
Auto-merging pkg/gce-pd-csi-driver/node.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"
Patch failed at 0001 fix: update Hyperdisk attach limits to match GCP documentation for Gen4 machines

In response to this:

/cherry-pick release-1.20

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