[lldb] Include "suspended" flag for Tasks

[kastiglione]

Display a "suspended" flag for Tasks in that state. The other main Task states, "enqueued", "running", and "complete", are already displayed.

From Swift's Task.h:

/// A task can have the following states:
///   * suspended: In this state, a task is considered not runnable
///   * enqueued: In this state, a task is considered runnable
///   * running on a thread
///   * completed

rdar://148663671

[kastiglione]

swiftlang/swift#82968
@swift-ci test