Get-AzApiManagementUser doesn't provide result if $filter parameter contains +

### Description

When the email prefix contains a '+', no result will return for the following command:
$apimUser = Get-AzApiManagementUser -Context $apimContext -Email $emailAddress

However, https://learn.microsoft.com/en-us/rest/api/apimanagement/current-ga/user/list-by-service works fine and found that it is related to encoding URL. Manually, encoding the parameter value such as $encodedEmail=[System.Web.HttpUtility]::UrlEncode("abc+@contoso.com") before passing works good.

Is this expected? If so, we may need to add this to docs.

Expected behavior:
Provide results for the user with that specific email address.

Example:
Body:
{
"value": [
{
"id": "/subscriptions/xxx/resourceGroups/xxx/providers/Microsoft.ApiManagement/service/xxx/users/abc-contoso-com",
"type": "Microsoft.ApiManagement/service/users",
"name": "abc-contoso-com",
"properties": {
"firstName": "ABC",
"lastName": "XYZ",
"email": "abc+@contoso.com",
"state": "active",
"registrationDate": "2023-06-12T16:37:32.647Z",
"note": null,
"identities": [
{
"provider": "Basic",
"id": "abc+@contoso.com"
}
]
}
}
],
"count": 1
}

### Script or Debug output

```PowerShell
Actual output:

Body:
{
"value": [],
"count": 0
}
```

### Environment data

_No response_

### Module versions

_No response_

### Error output

_No response_

Start at the Get-AzApiManagementUser cmdlet and reproduce the email filter behavior with an address containing '+'. Compare the request with the User - List By Service REST endpoint, then verify that the cmdlet returns the matching user without requiring callers to pre-encode the email.

Written by the indexing model from the issue text.