Content Model: Improve cache behavior

[JiuqingSong]

• Move allowCacheElement from DomToModelFormatContext to EditorContext, so we will only allow cache element in Content Model when create content model from editor
• Remove disableCacheElement from DomToModelOption since now we always allow cache element for Content Model from editor, and always disallow cache element when create Content Model from other sources
• In API cloneModel, add an options parameter, and now by default cachedElement will not be included in cloned model. For entity and general model, we will put a cloned element as the wrapper element. We will include cached element and directly put the same reference to entity only when options.includeCachedElement is true. So that when clone model for cut/copy, the new model can be fully disconnected from editor content
• Fix some selection bugs in ContentModelCopyPastePlugin
• Fix Content Model: "Copy" can delete entity #1997, copy content using Content Model won't make entity disappear even cached model is used
• Use common API formatWithContentModel for cut action in ContentModelCopyPastePlugin
• Fix all related test cases

[BryanValverdeU]

It seems that copying a entity is changing the color and the background color.

<div>asdsadsad&nbsp;<span class="entityDelimiterBefore">​</span><span style="display: inline-block;" class="_Entity _EType_asdasd _EId_asdasd_35 _EReadonly_1" contenteditable="false"><span>| entity |</span></span><span class="entityDelimiterAfter">​</span>&nbsp;asdsadsadsad</div><!--{"type":0,"isDarkMode":true,"start":[0,0,0],"end":[0,4,13]}-->

With this change, copying and pasting the first line

Before

[JiuqingSong]

It seems that copying a entity is changing the color and the background color.

<div>asdsadsad&nbsp;<span class="entityDelimiterBefore">​</span><span style="display: inline-block;" class="_Entity _EType_asdasd _EId_asdasd_35 _EReadonly_1" contenteditable="false"><span>| entity |</span></span><span class="entityDelimiterAfter">​</span>&nbsp;asdsadsadsad</div><!--{"type":0,"isDarkMode":true,"start":[0,0,0],"end":[0,4,13]}-->

With this change, copying and pasting the first line

Before

Thanks for caching this. I fixed it by adding it back into handleEntity.

Now entity model will always have the original wrapper element, and we only handle the separation when

1. clone model
2. write back