feat(dds): support primary standby switch

[saf3dfsa]

What this PR does / why we need it: support primary standby switch

PR Checklist

• [x] Tests added/passed.

make testacc TEST="./huaweicloud/services/acceptance/dds" TESTARGS="-run TestAccDDSPrimaryStandbySwitch_"
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud/services/acceptance/dds -v -run TestAccDDSPrimaryStandbySwitch_ -timeout 360m -parallel 4
=== RUN   TestAccDDSPrimaryStandbySwitch_basic
=== PAUSE TestAccDDSPrimaryStandbySwitch_basic
=== RUN   TestAccDDSPrimaryStandbySwitch_node
=== PAUSE TestAccDDSPrimaryStandbySwitch_node
=== CONT  TestAccDDSPrimaryStandbySwitch_node
=== CONT  TestAccDDSPrimaryStandbySwitch_basic
--- PASS: TestAccDDSPrimaryStandbySwitch_basic (794.44s)
--- PASS: TestAccDDSPrimaryStandbySwitch_node (803.02s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/dds       803.074s

• [x] Documentation updated.

• [x] Schema updated.

• [ ] CheckDeleted.

  • a. During query operation (Read Context) aa. Resource not found >>>>>> Paste the screenshot here <<<<<<

  • b. During delete/disassociate/unbind operation (Delete Context) ba. Resource not found >>>>>> Paste the screenshot here <<<<<<