Update Advanced Connections Settings panel default values

[croblesm]

Add the following default values for the following options:

setting	value
Connection timeout	15 seconds
Application name	vscode-mssql

I also found another reference to the Application name in the User settings (JSON)

"mssqlOptions": {
    "appName": "SQLTools",
    "useUTC": true,
    "encrypt": true
}

Also consider updated the Connection timeout label, adding the support text seconds:
Connection timeout (seconds)

[croblesm]

Tagging @jdesai-24 for visibility