feat(cfw): add this data source to get the list of CFW tags

[profoundwu]

What this PR does / why we need it:
add this data source to get the list of CFW tags
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 this data source to get the list of CFW tags

PR Checklist

• Tests added/passed.

make testacc TEST="./huaweicloud/services/acceptance/cfw" TESTARGS="-run TestAccDataSourceC
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud/services/acceptance/cfw -v -run TestAccDataSourceCfwTags_basic -timeout 360m -parallel 4
=== RUN   TestAccDataSourceCfwTags_basic
=== PAUSE TestAccDataSourceCfwTags_basic
=== CONT  TestAccDataSourceCfwTags_basic
--- PASS: TestAccDataSourceCfwTags_basic (16.11s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/cfw       16.192s

• 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 <<<<<<

[Alice1319]

LGTM

[dengyali0125]

LGTM

[WangLiNaruto]

LGTM

[houpeng80]

/lgtm

[luoping-12345]

LGTM

[Jason-Zhang9309]

/approve

[github-ci-robot]

This PR has been approved by: @Jason-Zhang9309

/approve