Fix GCE instance update issue where initializeParams is sent for exis…

[mskrynnik]

Fixes validation errors during google_compute_instance updates for VMs using hyperdisk-balanced boot disks.

Problem Description

When performing updates on a google_compute_instance, the provider performs a GET-modify-PUT flow. The GCE API returns initializeParams in its GET responses for existing attached disks under certain conditions. When this payload is sent back during instances.update PUT requests, GCE's backend validator parses initializeParams as a disk creation/modification action, failing with:
Provisioned IOPS cannot be specified with disk type pd-balanced

Solution

This PR strips the initializeParams block from all disks in the instance map (instMap) prior to sending GCE instances.update PUT requests. Since initializeParams is input-only and cannot be updated on existing disks, removing it is safe and backward compatible.

Verification

Modified TestAccComputeInstance_hyperdiskBootDisk_provisioned_iops_throughput to include an update step (description change), and verified that it builds and passes successfully.
Resolves: b/509846156

Release Note Template for Downstream PRs (will be copied)

See Write release notes for guidance.

compute: fixed a validation error on `google_compute_instance` (`Provisioned IOPS cannot be specified with disk type pd-balanced`) that occurred during updates on instances with Hyperdisk Balanced boot disks.

[github-actions]

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[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes for commit 4a2b413:

Diff report

Your PR generated the following diffs in downstream repositories:

Repository	Diff Link	Changes
google provider	View Diff	3 files changed, 53 insertions(+)
google-beta provider	View Diff	3 files changed, 55 insertions(+)
terraform-google-conversion	View Diff	2 files changed, 20 insertions(+)

Test report

Analytics

Total Tests	Passed	Skipped	Affected
1474	1380	93	1

Affected Service Packages

• compute

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• TestAccComputeInstance_hyperdiskBootDisk_provisioned_iops_throughput

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Recording Mode	Replaying Rerun	Test Name
✅ Log	✅	TestAccComputeInstance_hyperdiskBootDisk_provisioned_iops_throughput

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@mskrynnik, @shuyama1 VCR tests complete for 4a2b413!