az sql db show-connection-string should accept username/password

**Is your feature request related to a problem? Please describe.**

When I call show-connection-string I want to supply the username and password, so I can just use the outputted string. Right now I have to run the command, copy that output to notepad, replace the values, and then use it.

**Describe the solution you'd like**

Allow me to specify the username/password and generate a full connection string.

**Describe alternatives you've considered**

**Additional context**

```
{
"azure-cli": "2.22.1",
"azure-cli-core": "2.22.1",
"azure-cli-telemetry": "1.0.6",
"extensions": {
"azure-devops": "0.18.0",
"fzf": "1.0.2",
"imds": "0.1.0",
"noelbundick": "0.0.17"
}
}
```

```
dotnetcore-sqldb-tutorial$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04.1 LTS
Release: 20.04
Codename: focal
```

ddcc1