[Feature][Test][Docs] Security group rule supports description parameter

[Lance52259]

What this PR does / why we need it:
Networking Security Group API supports description set and update operation, these actions can be supported by huaweicloud porvider.

Which issue this PR fixes:
(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)
fixes #905

Special notes for your reviewer:

Release note:

1. add description parameter to provider schema, document and acc test.

PR Checklist

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

Acceptance Steps Performed

make testacc TEST='./huaweicloud' TESTARGS='-run=TestAccNetworkingV2SecGroupRule_basic'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud -v -run=TestAccNetworkingV2SecGroupRule_basic -timeout 360m -parallel 4
=== RUN   TestAccNetworkingV2SecGroupRule_basic
=== PAUSE TestAccNetworkingV2SecGroupRule_basic
=== CONT  TestAccNetworkingV2SecGroupRule_basic
--- PASS: TestAccNetworkingV2SecGroupRule_basic (48.43s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud       48.476s