Add support for breakpoints alter hook

Problem/Motivation

Breakpoints that are provided by themes and modules can be altered. ECA should support that feature.

Proposed resolution

An event/hook is required:

  /**
   * Implements hook_breakpoints_alter().
   */
  #[Hook('breakpoints_alter')]
  public function breakpointsAlter(array $definitions): void {
  }

In addition to that, also 3 action plugins are required:

• Create new breakpoint
• Update breakpoint
• Delete breakpoint