add cdn datasource

[crab21]

$ make testacc TESTARGS=" -run=TestAccTencentCloudCdnDomains"
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./... -v -run=TestAccTencentCloudCdnDomains -timeout 120m
? github.com/terraform-providers/terraform-provider-tencentcloud [no test files]
testing: warning: no tests to run
PASS
ok github.com/terraform-providers/terraform-provider-tencentcloud/gendoc 1.438s [no tests to run]
=== RUN TestAccTencentCloudCdnDomains
--- PASS: TestAccTencentCloudCdnDomains (212.71s)
PASS
ok github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud 214.189s
? github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud/connectivity [no test files]
? github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud/internal/helper [no test files]
? github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud/ratelimit [no test files]

[crab21]

add cdn domain result fileds.

---

$ make testacc TESTARGS=" -run=TestAccTencentCloudCdnDomains"
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./... -v -run=TestAccTencentCloudCdnDomains -timeout 120m
? github.com/terraform-providers/terraform-provider-tencentcloud [no test files]
testing: warning: no tests to run
PASS
ok github.com/terraform-providers/terraform-provider-tencentcloud/gendoc (cached) [no tests to run]
=== RUN TestAccTencentCloudCdnDomains
--- PASS: TestAccTencentCloudCdnDomains (134.77s)
PASS
ok github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud 135.981s
? github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud/connectivity [no test files]
? github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud/internal/helper [no test files]
? github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud/ratelimit [no test files]

[crab21]

remove redundancy code and add offset field.

---

$ make testacc TESTARGS=" -run=TestAccTencentCloudCdnDomains"
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./... -v -run=TestAccTencentCloudCdnDomains -timeout 120m
? github.com/terraform-providers/terraform-provider-tencentcloud [no test files]
testing: warning: no tests to run
PASS
ok github.com/terraform-providers/terraform-provider-tencentcloud/gendoc 0.921s [no tests to run]
=== RUN TestAccTencentCloudCdnDomains
--- PASS: TestAccTencentCloudCdnDomains (121.35s)
PASS
ok github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud 121.978s
? github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud/connectivity [no test files]
? github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud/internal/helper [no test files]
? github.com/terraform-providers/terraform-provider-tencentcloud/tencentcloud/ratelimit [no test files]