"az mysql flexible-server import create "doesn't support subnet with multiple address prefix.

### Describe the bug

the command "az mysql flexible-server import create " didn't support subnet with multiple address prefix.
if a subnet has a multiple address prefix ,it will cause the command error.

"subnets": [
{
"name": "mysql",

"properties": {
"provisioningState": "Succeeded",
"addressPrefixes": [
"10.5.0.0/24"
],
"delegations": [],
"privateEndpointNetworkPolicies": "Disabled",
"privateLinkServiceNetworkPolicies": "Enabled"
},
"type": "Microsoft.Network/virtualNetworks/subnets"
}
]

### Related command

az mysql flexible-server import create

### Errors

cli.azure.cli.core.azclierror: The command failed with an unexpected error. Here is the traceback:
az_command_data_logger: The command failed with an unexpected error. Here is the traceback:
cli.azure.cli.core.azclierror: 'addressPrefix'
Traceback (most recent call last):
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\knack/cli.py", line 233, in invoke
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 664, in execute
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 731, in _run_jobs_serially
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 701, in _run_job
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 334, in __call__
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/command_operation.py", line 121, in handler
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/custom.py", line 570, in flexible_server_import_create
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/custom.py", line 1125, in flexible_server_provision_network_resource
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/_network.py", line 126, in prepare_private_network
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/_network.py", line 155, in process_private_network_with_id_input
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/_network.py", line 213, in _create_vnet_subnet_delegation
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/_network.py", line 226, in _create_subnet_delegation
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/_network.py", line 226, in
KeyError: 'addressPrefix'
az_command_data_logger: 'addressPrefix'
Traceback (most recent call last):
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\knack/cli.py", line 233, in invoke
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 664, in execute
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 731, in _run_jobs_serially
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 701, in _run_job
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 334, in __call__
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/command_operation.py", line 121, in handler
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/custom.py", line 570, in flexible_server_import_create
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/custom.py", line 1125, in flexible_server_provision_network_resource
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/_network.py", line 126, in prepare_private_network
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/_network.py", line 155, in process_private_network_with_id_input
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/_network.py", line 213, in _create_vnet_subnet_delegation
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/_network.py", line 226, in _create_subnet_delegation
File "D:\a\_work\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/mysql/_network.py", line 226, in
KeyError: 'addressPrefix'
To check existing issues, please visit: https://github.com/Azure/azure-cli/issues

### Issue script & Debug output

cli.azure.cli.core.sdk.policies: Response content:
cli.azure.cli.core.sdk.policies: {
"name": "dbnet",

"type": "Microsoft.Network/virtualNetworks",
"location": "northeurope",
"tags": {},
"properties": {
"provisioningState": "Succeeded",

"addressSpace": {
"addressPrefixes": [
"10.0.0.0/16"
]
},

"subnets": [
{
"name": "dbsubnet",


"properties": {
"provisioningState": "Succeeded",
"addressPrefixes": [
"10.0.1.0/24"
],

],
"virtualNetworkPeerings": [],
"enableDdosProtection": false
}
}

### Expected behavior

az mysql flexible-server import create

### Environment Summary

{
"azure-cli": "2.58.0",
"azure-cli-core": "2.58.0",
"azure-cli-telemetry": "1.1.0",
"extensions": {
"account": "0.2.5",
"arcdata": "1.5.13",
"databricks": "0.10.2"
}
}

### Additional context

_No response_