Migrate data_source_google_compute_instance_serial_port.go data source to use direct HTTP rather than a client library

[GitOleksandrBokov]

Part of the ongoing migration of handwritten compute files from the Apiary client library to direct HTTP calls (transport_tpg.SendRequest). Same pattern as #18444 and the merged data source migrations #17090 / #17117.

• Replaces NewClient(...).Instances.GetSerialPortOutput(project, zone, instance).Port(port).Do() with GET projects/{project}/zones/{zone}/instances/{instance}/serialPort?port=N via transport_tpg.SendRequest + transport_tpg.AddQueryParams.
• Error handling is unchanged: the call had no 404 handler before and still returns the raw error.
• No schema, test, or documentation changes. The recorded VCR cassette stays replay-compatible: after the matcher strips alt/prettyPrint, both the old and the new request reduce to the same URL with port=N.

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compute: migrated `google_compute_instance_serial_port` data source to use direct HTTP rather than a client library

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes for commit 3d84cb7:

Diff report

Your PR generated the following diffs in downstream repositories:

Repository	Diff Link	Changes
google provider	View Diff	1 file changed, 18 insertions(+), 4 deletions(-)
google-beta provider	View Diff	1 file changed, 18 insertions(+), 4 deletions(-)

Test report

Analytics

Total Tests	Passed	Skipped	Affected
1555	1458	95	2

Affected Service Packages

• compute

Learn how VCR tests work

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Step 1: Replaying Mode

Action taken

Found 2 affected test(s) by replaying old test recordings. Starting RECORDING based on the most recent commit.

Click here to see the affected tests

• TestAccComputeInstanceFromMachineImage_diffProject
• TestAccComputeSecurityPolicy_withPreconfiguredWafConfig

View the replaying VCR build log

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Step 2: Recording Mode

Recording Mode	Replaying Rerun	Test Name
❌ Error · Log	-	TestAccComputeInstanceFromMachineImage_diffProject
❌ Error · Log	-	TestAccComputeSecurityPolicy_withPreconfiguredWafConfig

Caution

Issues requiring attention before PR completion

🔴 Initial Recording Failed: Some tests failed during the recording step. See the table above for details.

Please address these issues to complete your PR. If you believe these detections are incorrect or unrelated to your change, please raise the concern with your reviewer.

View the recording VCR build log or the debug logs folder for detailed results.

@GitOleksandrBokov VCR tests complete for 3d84cb7!