feat(GaussDB): gaussdb redis instance support mode

[houpeng80]

What this PR does / why we need it: gaussdb redis instance support mode 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:

  gaussdb redis instance support mode

PR Checklist

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

Acceptance Steps Performed

make testacc TEST=./huaweicloud/services/acceptance/gaussdb/ TESTARGS='-run TestAccGaussRedisInstance_'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud/services/acceptance/gaussdb/ -v -run TestAccGaussRedisInstance_ -timeout 360m -parallel 4
=== RUN   TestAccGaussRedisInstance_basic
=== PAUSE TestAccGaussRedisInstance_basic
=== RUN   TestAccGaussRedisInstance_withReplication
=== PAUSE TestAccGaussRedisInstance_withReplication
=== RUN   TestAccGaussRedisInstance_updateWithEpsId
=== PAUSE TestAccGaussRedisInstance_updateWithEpsId
=== CONT  TestAccGaussRedisInstance_basic
=== CONT  TestAccGaussRedisInstance_updateWithEpsId
=== CONT  TestAccGaussRedisInstance_withReplication
=== CONT  TestAccGaussRedisInstance_updateWithEpsId
    acceptance.go:531: The environment variables does not support Migrate Enterprise Project ID for acc tests
--- SKIP: TestAccGaussRedisInstance_updateWithEpsId (0.00s)
--- PASS: TestAccGaussRedisInstance_withReplication (1269.40s)
--- PASS: TestAccGaussRedisInstance_basic (3449.67s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/gaussdb   3449.722s

[github-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This PR has been approved by: @houpeng80

[Jason-Zhang9309]

/lgtm