chore(waf): modify some issues with the waf certificate resource and datasource

[deer-hang]

What this PR does / why we need it:

• modify waf certificate datasource and fix some problems.
  • fix some problems in datasource code.
  • support new filter fields in datasource.
  • discard two invalid fields.
  • refactor datasource code to automatically generate styles.
  • supplementary datasource documentation description.
  • improve test case execution efficiency.
• modify waf certificate resource and fix some problems.

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

• Tests added/passed.

make testacc TEST='./huaweicloud/services/acceptance/waf' TESTARGS='-run TestAccDataSourceWafCertificate_basic'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud/services/acceptance/waf -v -run TestAccDataSourceWafCertificate_basic -timeout 360m -parallel 4
=== RUN   TestAccDataSourceWafCertificate_basic
=== PAUSE TestAccDataSourceWafCertificate_basic
=== CONT  TestAccDataSourceWafCertificate_basic
--- PASS: TestAccDataSourceWafCertificate_basic (13.15s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/waf       13.191s

make testacc TEST='./huaweicloud/services/acceptance/waf' TESTARGS='-run TestAccWafCertificate_basic'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud/services/acceptance/waf -v -run TestAccWafCertificate_basic -timeout 360m -parallel 4
=== RUN   TestAccWafCertificate_basic
=== PAUSE TestAccWafCertificate_basic
=== CONT  TestAccWafCertificate_basic
--- PASS: TestAccWafCertificate_basic (18.88s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/waf       18.928s

• Documentation updated.

• 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 <<<<<<

[github-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This PR has been approved by: @deer-hang

[jinyangyang222]

/lgtm