Make sure all callbacks in registerCommand return objects properly

[michael-weng]

Describe the bug
Found this when implementing (#1144)
function commands.registerCommand(command: string, callback: (...args: any[]) => any, thisArg?: any): vscode.Disposable
As show the callback param can return type any, and if we are not care with implicit return of arrow function expressions it's easy to miss this and as a result execute command will not be able to return the promise as expected.

example:
vscode.commands.registerCommand(COMMANDS.UseLocalDependency, item => {
if (item instanceof PackageNode) {
useLocalDependency(item.name, ctx);
}
}),

the above should return the promise returned by useLocalDependency

Expected behavior
All executeCommand of registered command properly return the right objects.

Environment

• Impact all platforms

[michael-weng]

This will be verified by #1144 passing.

[award999]

To resister command callbacks return is propagated but the callback itself may not return anything