Add command to switch "autobuild" on/off

Hi,

most of the time I run maven build outside of vscode in the terminal. This interferes with the extension's way of detecting changes. It seems that the extension also starts building, which leads to alot of ClassNotFoundExceptions in the maven build (probably because vscode deleted the already build classes while the maven build was running).

To circumvent this I used to temporarily disable the auto build feature back when I was using Eclipse.
I know this is also possible via the settings menu.

Environment

• Operating System: macOS 11.5.1 (20G80)
• JDK version: openjdk version "15" 2020-09-15
• Visual Studio Code version: 1.60.0-insider
• Java extension version: v0.18.2

Steps To Reproduce

1. Start a long running maven build (something simple will not work)
2. See ClassNotFoundExceptions in the maven build

Expected Result

• Add the `Autobuild: Enabled/Disabled" settings to the command pallet
• Add the `Autobuild: Enabled/Disabled" to the status bar, at least to show the status, better even to allow to toggle the setting.

This would allow to easily switch between those two modes.

L'issue indica l'impostazione autobuild esistente e la sua implementazione in settings-menu; inizia individuando tale impostazione e le registrazioni dei comandi e della barra di stato dell'estensione. Verifica la riproduzione di lunga durata di Maven, quindi conferma che l'impostazione possa essere attivata o disattivata dalla Command Palette e dalla barra di stato e che il suo stato abilitato o disabilitato sia visibile.