[!!!][FEATURE] Refactor/reintroduce table.t3-table

Bring a central/common table style "t3-table".
Refactor the pre-existing CSS code.

All backend tables that display tabular table data
should use the CSS class .t3-table.

HTML code:

<table class="t3-table">
  <thead>
    <tr>
      <th>...</th>
      <th>...</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td class="t3-table-tree"><img src="Icon" /></td>
      <td>...</td>
    </tr>
  </tbody>
</table>

This patch makes .t3-row-header & .typo3_dblist unnecessary.

Change-Id: Ic7e66fd1d6e8b9cc541133f1216f26ae7d8d09cf
Resolves: #52558
Related: #49592
Releases: 6.2
Reviewed-on: https://review.typo3.org/24425
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring