Backport of test: use T.TempDir to create temporary test directory into release/1.3.x

[hc-github-team-nomad-core]

Backport

This PR is auto-generated from #12853 to be assessed for backporting due to the inclusion of the label backport/1.3.x.

The below text is copied from the body of the original PR.

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A testing cleanup.

This pull request replaces ioutil.TempDir with t.TempDir. We can use the T.TempDir function from the testing package to create temporary directory. The directory created by T.TempDir is automatically removed when the test and all its subtests complete.

This saves us at least 2 lines (error check, and cleanup) on every instance, or in some cases adds cleanup that we forgot.

Reference: https://pkg.go.dev/testing#T.TempDir

func TestFoo(t *testing.T) {
	// before
	tmpDir, err := ioutil.TempDir("", "")
	require.NoError(t, err)
	defer require.NoError(t, os.RemoveAll(tmpDir))

	// now
	tmpDir := t.TempDir()
}

Related PR in Terraform: hashicorp/terraform#30803

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