feat(rgc): add new resource RGC account

[Jason-Zhang9309]

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.

make testacc TEST='./huaweicloud/services/acceptance/rgc' TESTARGS='-run TestAccAccount_basic'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud/services/acceptance/rgc -v -run TestAccAccount_basic -timeout 360m -parallel 4
=== RUN   TestAccAccount_basic
=== PAUSE TestAccAccount_basic
=== CONT  TestAccAccount_basic
--- PASS: TestAccAccount_basic (402.53s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/rgc       402.589s

• [x] Documentation updated.
• [x] Schema updated.

• [x] 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 <<<<<< account has been un-enrolled account has been closed

[github-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This PR has been approved by: @Jason-Zhang9309

[houpeng80]

/lgtm