feat(drag-drop): cdkConnectedTo finds all drop lists with the same ID, instead of only one

Feature Description

CdkDropList has id and cdkConnectedTo input properties to allow specifying an id or array of ids for which the drop lists should be connected.

The id input property "needs" to be unique, or better put is "assumed" to be unique - meaning when searching through drop lists to connect to by id, only the first match is returned.

Can the "need" for unique ids be removed and change the connected drop list logic to return all drop lists with a matching id?

From the user's perspective:

• If I want a drop list to inherently be standalone, provide a unique id.
• If I want a drop list to inherently be connected to others, provide a shared id.

Use Case

Connecting drop lists created dynamically, possibly defined in separate template files and with arbitrary DOM relation, without the overhead of having to maintain a separate list of all drop lists that should be connected, and making sure this list is properly updated and propagated to each drop list via change detection.

Instead a statically defined (or could be dynamic) id for the id and cdkConnectedTo inputs will automatically connect all the drop lists without any further coordination from the user.

Similar to what @sroettering mentioned here, but I don't think a new input property is necessary.

首先定位 CdkDropList 的实现及其测试，然后跟踪 id 和 cdkConnectedTo 如何解析已连接的放置列表。更新行为，使共享的 id 能解析所有匹配的列表，并验证唯一的 id 仍保持独立，而共享的 id 会连接每个匹配的列表。