Added support of `customer_managed_key` into `azurerm_cognitive_account`

[dkuzmenok]

Description

Currently customer_managed_key in a Cognitive Account can be used only as a separate resource azurerm_cognitive_account_customer_managed_key.

This makes impossible to create azurerm_cognitive_account with use of CMK from the very beginning.

Changes

This PR is adding a support of customer_managed_key in azurerm_cognitive_account.

Resolves #18084.

Tests

# go test -v -timeout 3000s -run ^TestAccCognitiveAccount github.com/hashicorp/terraform-provider-azurerm/internal/services/cognitive/
=== RUN   TestAccCognitiveAccountCustomerManagedKey_basic
=== PAUSE TestAccCognitiveAccountCustomerManagedKey_basic
=== RUN   TestAccCognitiveAccountCustomerManagedKey_requiresImport
=== PAUSE TestAccCognitiveAccountCustomerManagedKey_requiresImport
=== RUN   TestAccCognitiveAccountCustomerManagedKey_complete
=== PAUSE TestAccCognitiveAccountCustomerManagedKey_complete
=== RUN   TestAccCognitiveAccountCustomerManagedKey_update
=== PAUSE TestAccCognitiveAccountCustomerManagedKey_update
=== RUN   TestAccCognitiveAccountDataSource_basic
=== PAUSE TestAccCognitiveAccountDataSource_basic
=== RUN   TestAccCognitiveAccount_basic
=== PAUSE TestAccCognitiveAccount_basic
=== RUN   TestAccCognitiveAccount_speechServices
=== PAUSE TestAccCognitiveAccount_speechServices
=== RUN   TestAccCognitiveAccount_requiresImport
=== PAUSE TestAccCognitiveAccount_requiresImport
=== RUN   TestAccCognitiveAccount_complete
=== PAUSE TestAccCognitiveAccount_complete
=== RUN   TestAccCognitiveAccount_update
=== PAUSE TestAccCognitiveAccount_update
=== RUN   TestAccCognitiveAccount_qnaRuntimeEndpoint
=== PAUSE TestAccCognitiveAccount_qnaRuntimeEndpoint
=== RUN   TestAccCognitiveAccount_qnaRuntimeEndpointUnspecified
=== PAUSE TestAccCognitiveAccount_qnaRuntimeEndpointUnspecified
=== RUN   TestAccCognitiveAccount_cognitiveServices
=== PAUSE TestAccCognitiveAccount_cognitiveServices
=== RUN   TestAccCognitiveAccount_withMultipleCognitiveAccounts
=== PAUSE TestAccCognitiveAccount_withMultipleCognitiveAccounts
=== RUN   TestAccCognitiveAccount_networkAclsVirtualNetworkRules
=== PAUSE TestAccCognitiveAccount_networkAclsVirtualNetworkRules
=== RUN   TestAccCognitiveAccount_networkAcls
=== PAUSE TestAccCognitiveAccount_networkAcls
=== RUN   TestAccCognitiveAccount_identity
=== PAUSE TestAccCognitiveAccount_identity
=== RUN   TestAccCognitiveAccount_metricsAdvisor
=== PAUSE TestAccCognitiveAccount_metricsAdvisor
=== RUN   TestAccCognitiveAccount_customerManagedKey
=== PAUSE TestAccCognitiveAccount_customerManagedKey
=== CONT  TestAccCognitiveAccountCustomerManagedKey_basic
=== CONT  TestAccCognitiveAccount_speechServices
=== CONT  TestAccCognitiveAccount_complete
=== CONT  TestAccCognitiveAccount_update
--- PASS: TestAccCognitiveAccount_complete (146.27s)
=== CONT  TestAccCognitiveAccount_networkAclsVirtualNetworkRules
--- PASS: TestAccCognitiveAccount_speechServices (172.80s)
=== CONT  TestAccCognitiveAccount_customerManagedKey
--- PASS: TestAccCognitiveAccount_update (209.71s)
=== CONT  TestAccCognitiveAccount_metricsAdvisor
--- PASS: TestAccCognitiveAccountCustomerManagedKey_basic (346.53s)
=== CONT  TestAccCognitiveAccount_identity
--- PASS: TestAccCognitiveAccount_networkAclsVirtualNetworkRules (311.24s)
=== CONT  TestAccCognitiveAccount_networkAcls
--- PASS: TestAccCognitiveAccount_customerManagedKey (292.68s)
=== CONT  TestAccCognitiveAccount_cognitiveServices
--- PASS: TestAccCognitiveAccount_cognitiveServices (110.19s)
=== CONT  TestAccCognitiveAccount_withMultipleCognitiveAccounts
--- PASS: TestAccCognitiveAccount_withMultipleCognitiveAccounts (122.00s)
=== CONT  TestAccCognitiveAccount_requiresImport
--- PASS: TestAccCognitiveAccount_networkAcls (319.45s)
--- PASS: TestAccCognitiveAccount_identity (451.14s)
=== CONT  TestAccCognitiveAccount_qnaRuntimeEndpointUnspecified
--- PASS: TestAccCognitiveAccount_requiresImport (169.22s)
=== CONT  TestAccCognitiveAccountCustomerManagedKey_update
--- PASS: TestAccCognitiveAccount_qnaRuntimeEndpointUnspecified (121.11s)
=== CONT  TestAccCognitiveAccount_basic
=== CONT  TestAccCognitiveAccountDataSource_basic
--- PASS: TestAccCognitiveAccount_basic (130.55s)
=== CONT  TestAccCognitiveAccountCustomerManagedKey_complete
--- PASS: TestAccCognitiveAccount_metricsAdvisor (842.50s)
=== CONT  TestAccCognitiveAccountCustomerManagedKey_requiresImport
--- PASS: TestAccCognitiveAccountDataSource_basic (123.16s)
=== CONT  TestAccCognitiveAccount_qnaRuntimeEndpoint
--- PASS: TestAccCognitiveAccountCustomerManagedKey_complete (293.89s)
--- PASS: TestAccCognitiveAccountCustomerManagedKey_update (489.91s)
--- PASS: TestAccCognitiveAccountCustomerManagedKey_requiresImport (321.67s)
--- PASS: TestAccCognitiveAccount_qnaRuntimeEndpoint (253.12s)
PASS
ok    github.com/hashicorp/terraform-provider-azurerm/internal/services/cognitive     1399.431s
#