feat(VPC): add params to vpc subnet resource

[houpeng80]

What this PR does / why we need it:
add params to vpc subnet resource
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:

  add params to vpc subnet resource

PR Checklist

• Tests added/passed.

make testacc TEST=./huaweicloud/services/acceptance/vpc/ TESTARGS='-run TestAccVpcSubnetV1_'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud/services/acceptance/vpc/ -v -run TestAccVpcSubnetV1_ -timeout 360m -parallel 4
=== RUN TestAccVpcSubnetV1_basic
=== PAUSE TestAccVpcSubnetV1_basic
=== RUN TestAccVpcSubnetV1_ipv6
=== PAUSE TestAccVpcSubnetV1_ipv6
=== RUN TestAccVpcSubnetV1_dhcp
=== PAUSE TestAccVpcSubnetV1_dhcp
=== CONT TestAccVpcSubnetV1_basic
=== CONT TestAccVpcSubnetV1_dhcp
=== CONT TestAccVpcSubnetV1_ipv6
--- PASS: TestAccVpcSubnetV1_basic (112.22s)
--- PASS: TestAccVpcSubnetV1_dhcp (112.59s)
--- PASS: TestAccVpcSubnetV1_ipv6 (121.85s)
PASS
ok github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/vpc 121.910s

* [ ] Documentation updated.
* [ ] Schema updated.
* [ ] CheckDeleted.

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

    <!-- If the resource depends the parent resource(s), please provide the related check result(s) of the CheckDeleted validation.
    ab. Related resources (parent resources) not found
    \>>>>>> Paste the screenshot here <<<<<<
    -->
  - **b. During delete/disassociate/unbind operation (Delete Context)**
    ba. Resource not found
    \>>>>>> Paste the screenshot here <<<<<<

    <!-- If the resource depends the parent resource(s), please provide the related check result(s) of the CheckDeleted validation.
    bb. Related resources (parent resources) not found
    \>>>>>> Paste the screenshot here <<<<<<
    -->

[github-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This PR has been approved by: @houpeng80

[Jason-Zhang9309]

/lgtm