Commands don't follow prefix rules *AzManagedCassandra*

### Description

Cmdlets need to have a prefix that's identity to their module name according to our design guideline. These cmdlets don't follow it.

### Issue script & Debug output

```PowerShell
PS C:\Users\yeliu [0.20s]> gcm *AzManagedCassandra*

CommandType Name Version Source
----------- ---- ------- ------
Cmdlet Get-AzManagedCassandraCluster 1.18.0 Az.CosmosDB
Cmdlet Get-AzManagedCassandraDatacenter 1.18.0 Az.CosmosDB
Cmdlet New-AzManagedCassandraCluster 1.18.0 Az.CosmosDB
Cmdlet New-AzManagedCassandraDatacenter 1.18.0 Az.CosmosDB
Cmdlet Remove-AzManagedCassandraCluster 1.18.0 Az.CosmosDB
Cmdlet Remove-AzManagedCassandraDatacenter 1.18.0 Az.CosmosDB
Cmdlet Update-AzManagedCassandraCluster 1.18.0 Az.CosmosDB
Cmdlet Update-AzManagedCassandraDatacenter 1.18.0 Az.CosmosDB
```

### Environment data

```PowerShell
N/A
```

### Module versions

```PowerShell
Az 13.5
but it's the same in latest repo
```

### Error output

```PowerShell
N/A
```

Start with the eight listed Get-, New-, Remove-, and Update-AzManagedCassandraCluster/Datacenter command entry points in the Az.CosmosDB module, then check the project's cmdlet prefix guideline. Update the affected command names consistently and rerun `gcm *AzManagedCassandra*` to confirm the published names follow the module prefix rule.

Written by the indexing model from the issue text.