List table: Select %s shouldn't be a row header

[afercia]

See related #31654 and #26167.

In all the List Tables in the admin, the "Select %s" (where %s is the name of the Post, Attachment, Plugin, User, etc,) is used as row header:

<th scope="row" class="check-column">

This is not correct from a semantics and accessibility point of view for all the reasons mentioned in #31654. The row header should be the cell with the main object the table refers to: the Post title, the Plugin name, etc.

We could also consider to use the abbr attribute: ​http://www.w3.org/TR/html5/tabular-data.html#attr-th-abbr
that would be consistent with what is currently proposed in sortable column headers ticket

[afercia]

One more good reason to address this issue is that, when a post is locked and the lock icon appears, the icon has no label or text that can be announced so screen readers will read out the column header "Select All";

[abcd95]

rought implementation

[abcd95]

Added in [15622]

This is a rough implementation and a thought put into existence. This doesn't account for the styling and CSS ruleset changes. I want opinions on whether this is the right direction to move forward.

Other list tables, such as the Users list and multi-site tables, are yet to be updated. Additionally, the styling has been affected, which I will address in the subsequent commits.

The styles of the plugins list table and highly coupled, and removing padding on unselected rows is affecting other headers. Debugging deeper into this -

​https://github.com/user-attachments/assets/40799432-d840-45df-a424-ca097078949d