Fix 335899: Split paragraph by BR before doing block format

[JiuqingSong]

When current paragraph has BR and do any paragraph format such as set indentation or bullet list, we need to split the paragraph by BR into multiple paragraphs then only format selected paragraphs.

For example:

<div>aaaa</div>
bbb<br>ccc<br>ddd<br>eee
<div>ffff</div>
<div>gggg</div>
hhh<br>iii<br>jjj
<div>kkk</div><!--{"type":"range","start":[3,2],"end":[13,1],"isReverted":false,"isDarkMode":false}-->

Before:

After:

Original bug: https://outlookweb.visualstudio.com/Outlook%20Web/_queries/edit/335899/?triage=true

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packages/roosterjs-content-model-api/lib/modelApi/block/splitSelectedParagraphByBr.ts:64

• [nitpick] The function name 'shallowColonParagraph' is not immediately descriptive; consider renaming it to something like 'cloneParagraph' or 'createParagraphCopy' to better convey its purpose.

function shallowColonParagraph(para: ReadonlyContentModelParagraph): ShallowMutableContentModelParagraph {