CCE cluster supports deleting associated items

[Lance52259]

What this PR does / why we need it:
CCE cluster API supports deleting associated items, such as efs, eni, evs, net, obs and sfs.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged):

NONE

Special notes for your reviewer:

Release note:

1. new enum value to select the associated resource to be deleted.

Acceptance Steps Performed

go test -v -run TestDeleteWithOptsV3Cluster
=== RUN   TestDeleteWithOptsV3Cluster
--- PASS: TestDeleteWithOptsV3Cluster (0.00s)
PASS
ok      github.com/huaweicloud/golangsdk/openstack/cce/v3/clusters/testing      0.019s

[coveralls]

Pull Request Test Coverage Report for Build 1200

• 16 of 18 (88.89%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 68.171%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
openstack/cce/v3/clusters/requests.go	16	18	88.89%

Totals
Change from base Build 1197:	0.02%
Covered Lines:	11559
Relevant Lines:	16956

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💛 - Coveralls