feat(vpcep): add new datasource to get VPC endpoint resource quota list

[ruwenqiang123]

What this PR does / why we need it:

Add a new data source to get VPC endpoint resource quota list.

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:

1.support a new data source to get the list of the VPC endpoint resource quotas.
2.support related document and acceptance test.

PR Checklist

• [x] Tests added/passed.

$ make testacc TEST="./huaweicloud/services/acceptance/vpcep" TESTARGS="-run TestAccDataSourceVpcepQuotas_basic"
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud/services/acceptance/vpcep -v -run TestAccDataSourceVpcepQuotas_basic -timeout 360m -parallel 4
=== RUN   TestAccDataSourceVpcepQuotas_basic
=== PAUSE TestAccDataSourceVpcepQuotas_basic
=== CONT  TestAccDataSourceVpcepQuotas_basic
--- PASS: TestAccDataSourceVpcepQuotas_basic (31.55s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/vpcep     31.640s

• [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 <<<<<<

[jinyangyang222]

/lgtm

[deer-hang]

/approve