WebUI: Add checkboxes for easy selection on mobile

[userwiths]

Closes #22701

Without checkboxes, mobile users cannot search and then select multiple tasks to delete.

I assume tasks refers to torrents until told otherwise.

Summary

Adds a setting that when turned ON renders a left most column that represents a checkbox in the torrents table

The state of this checkbox updates on torrent select/deselect to highlight the currently selected torrents

Checking/Unchecking the box allows for easier management of multiple torrents through a touch-screen device where selecting multiple non sequential torrents is more difficult than when using a mouse.

Notes

1. The condition for updating a row's content relies on a change in the response its getting from the server. Here we try to change that by introducting the jsManaged (boolean) attribute in to the column object, which would be false by default, but in case it is true we will trigger the column's updateTd regardless of change in server response.
2. DynamicTable.selectAll & DynamicTable.deselectAll did not trigger the event (onSelectedRowChanged) that selectRow and its related do, might have been done with performance in mind, dont have that much torrents to test with. Made it fire the events in order to be able to detect selection of all torrents.
3. Added an early return on the touchstart event of dynamicTableDiv. On desktop all was good, but on mobile this event fires together with the checkbox click and effectively deselects the selected row causing the checkbox to "blink" on for a second and then become unchecked again.

[glassez]

I wouldn't expect WebUI exclusive feature touches main (server) app in any way. Why not store this setting at the WebUI side?

[userwiths]

Agreed, latest version introduces this option only in the WebUI and does not change any server/app files.