Add migration center import job resource and tests

[slevenick]

Release Note Template for Downstream PRs (will be copied)

See Write release notes for guidance.

`google_migration_center_import_job`

[slevenick]

Depends on #17578

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes for commit 388f303:

Diff report

Your PR generated the following diffs in downstream repositories:

Repository	Diff Link	Changes
google provider	View Diff	5 files changed, 2781 insertions(+)
google-beta provider	View Diff	5 files changed, 2781 insertions(+)
terraform-google-conversion	View Diff	1 file changed, 152 insertions(+)
Open in Cloud Shell	View Diff	4 files changed, 117 insertions(+)

Test report

Analytics

Total Tests	Passed	Skipped	Affected
12	11	0	1

Affected Service Packages

• migrationcenter

Learn how VCR tests work

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Step 1: Replaying Mode

Action taken

Found 1 affected test(s) by replaying old test recordings. Starting RECORDING based on the most recent commit.

Click here to see the affected tests

• TestAccMigrationCenterImportJob_migrationCenterImportJobBasicExample

View the replaying VCR build log

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Step 2: Recording Mode

Recording Mode	Replaying Rerun	Test Name
✅ Log	✅	TestAccMigrationCenterImportJob_migrationCenterImportJobBasicExample

🟢 All tests passed!

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

@slevenick VCR tests complete for 388f303!

[melinath]

LGTM, looks straightforward!