feat(DEW): add a DataSource to query the CSMS secret

[Zippo-Wang]

What this PR does / why we need it:
import DEW resource, unit test and document.

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.
• Documentation updated.
• Schema updated.

Acceptance Steps Performed

=== RUN   TestAccDewCsmsSecretVersion_basic
=== PAUSE TestAccDewCsmsSecretVersion_basic
=== CONT  TestAccDewCsmsSecretVersion_basic
--- PASS: TestAccDewCsmsSecretVersion_basic (48.92s)
PASS

coverage: 8.2% of statements in ../../../../../terraform-provider-g42cloud/...

[github-ci-robot]

PR needs rebase.

[chengxiangdong]

/retitle feat(DEW): add a DataSource to query the CSMS secret

[chengxiangdong]

/lgtm
/approve