refactor(cdn): make ForceNew of name configurable

[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:

1. add common func FlexibleForceNew to make the ForceNew action configurable
2. use this func in cdn domain resource as an example

PR Checklist

• Tests added/passed.
• Documentation updated.
• Schema updated.

Acceptance Steps Performed

make testacc TEST='./huaweicloud/services/acceptance/cdn' TESTARGS='-run TestAccCdnDomain_basic'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud/services/acceptance/cdn -v -run TestAccCdnDomain_basic -timeout 360m -parallel 4
=== RUN   TestAccCdnDomain_basic
=== PAUSE TestAccCdnDomain_basic
=== CONT  TestAccCdnDomain_basic
--- PASS: TestAccCdnDomain_basic (704.94s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/cdn       704.991s

[github-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This PR has been approved by: @Jason-Zhang9309

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[github-ci-robot]

You are the author and cannot comment /lgtm

[Jason-Zhang9309]

/hold

[deer-hang]

Rename file name from forceNew.go to force_new.go

[deer-hang]

Add test cases for changes in the config directory.

[github-ci-robot]

This PR needs rebase.