feat(vpc): add a datasource to get a list of VPC IP address groups

[chengxiangdong]

What this PR does / why we need it:

Which issue this PR fixes: (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged) fixes #xxx

Special notes for your reviewer:

Release note:

PR Checklist

• [x] Tests added/passed.
• [x] Documentation updated.
• [x] Schema updated.

Acceptance Steps Performed

make testacc TEST='./huaweicloud/services/acceptance/vpc' TESTARGS='-run TestAccDataSourceVpcAddressGroups'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud/services/acceptance/vpc -v -run TestAccDataSourceVpcAddressGroups -timeout 360m -parallel 4
=== RUN   TestAccDataSourceVpcAddressGroups_basic
=== PAUSE TestAccDataSourceVpcAddressGroups_basic
=== CONT  TestAccDataSourceVpcAddressGroups_basic
--- PASS: TestAccDataSourceVpcAddressGroups_basic (15.61s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/vpc       15.693s