[Fix] Bucket_domain_name can be generated correctly by provider configuration

[Lance52259]

What this PR does / why we need it:

• Bucket_domain_name cannot be generated correctly by cloud and endpoint setting.
  • Bucket_domain_name is composed of bucket_name, region and cloud but the current cloud configuration cannot be applied to the cloud part.

Which issue this PR fixes:
(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)
fixes #957

Special notes for your reviewer:

Release note:

1. use cloud parameter to build bucket_domain_name when cloud is setting in provider config.

PR Checklist

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

Acceptance Steps Performed

provider configuration

provider "huaweicloud" {
  auth_url     = "https://iam.ru-moscow-1.hc.sbercloud.ru"
  cloud        = "hc.sbercloud.ru"
  domain_name  = "***"
  region       = "***"
  project_name = "***"
  access_key   = "***"
  secret_key   = "***"
  endpoints = {
    iam = "iam.ru-moscow-1.hc.sbercloud.ru"
    ecs = "ecs.ru-moscow-1.hc.sbercloud.ru"
    obs = "obs.ru-moscow-1.hc.sbercloud.ru"
  }
}

terraform apply

An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
  + create

Terraform will perform the following actions:

  # huaweicloud_obs_bucket.bucket will be created
  + resource "huaweicloud_obs_bucket" "bucket" {
      + acl                   = "private"
      + bucket                = "tf-test-bucket-demo-0302"
      + bucket_domain_name    = (known after apply)
      + enterprise_project_id = (known after apply)
      + force_destroy         = false
      + id                    = (known after apply)
      + policy                = (known after apply)
      + policy_format         = "obs"
      + quota                 = 0
      + region                = "ru-moscow-1"
      + storage_class         = "STANDARD"
      + versioning            = false
    }

Plan: 1 to add, 0 to change, 0 to destroy.

Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

  Enter a value: yes

huaweicloud_obs_bucket.bucket: Creating...
huaweicloud_obs_bucket.bucket: Creation complete after 7s [id=tf-test-bucket-demo-0302]

terraform show

# huaweicloud_obs_bucket.bucket:
resource "huaweicloud_obs_bucket" "bucket" {
    acl                = "private"
    bucket             = "tf-test-bucket-demo-0302"
    bucket_domain_name = "tf-test-bucket-demo-0302.obs.ru-moscow-1.hc.sbercloud.ru"
    force_destroy      = false
    id                 = "tf-test-bucket-demo-0302"
    policy_format      = "obs"
    quota              = 0
    region             = "ru-moscow-1"
    storage_class      = "STANDARD"
    versioning         = false
}