Clean'up `pt` and `%` handling in table columns after pasting from MSExcel

[arkflpc]

This is not triggering column width normalization for such case:

<table>
    <colgroup>
        <col style="width: 30pt;">
        <col style="width: 70pt;">
    </colgroup>
    <tbody>
        <tr>
            <td>a</td>
            <td>b</td>
        </tr>
    </tbody>
</table>

And the final table ends up like this:

<figure class="table">
    <table class="ck-table-resized">
        <colgroup>
            <col style="width:30%;">
            <col style="width:70%;">
        </colgroup>
        <tbody>
        <tr>
            <td>a</td>
            <td>b</td>
        </tr>
        </tbody>
    </table>
</figure>

So pt values are treated as they would be %, the table gets full page width and the original sizes are not preserved.

The column width is normalized in post-fixer (but should be normalized before post-fixers are triggered).

Originally posted by @niegowski in https://github.com/ckeditor/ckeditor5/pull/14720#discussion_r1304715937

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