Add a hidden column to the network table to allow filtering by hostnames

[rdwebdesign]

What does this PR aim to accomplish?

This PR restores v5 functionality, allowing users to filter the Network table using hostnames.

The v5 table had a hostname column, allowing datatables to use the values on this column to filter the table.
In v6 this column was merged with IP column; The hostnames are dynamically added to the first cell, but they are not searchable.

Issue originally reported on Discourse:
https://discourse.pi-hole.net/t/search-in-tools-network-not-searching-on-hostname-v6/77123

How does this PR accomplish the above?

Including a hidden column containing the hostnames allows datatables to use these values.

Note:
When saveState is true, datatables ignores visible: false and shows the column. If we set saveState: false we lose the ability to save properties like sort order, number of items per page, etc.

To solve this issue, we keep saveState: true and use class: "hide", to make sure the column will be hidden by CSS .hide class.

Link documentation PRs if any are needed to support this PR:

none

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