Frontend: the device test cannot see a blocker that stops the plugin's own scripts #2062

Problem

The device test (/valid/?ffc_device_check=1) does not report several ways a content blocker, an optimizer or a firewall stops the plugin:

• The test itself does not run. A blocker, or a broken combined file (as the LiteSpeed case in Frontend: LiteSpeed's minifier cuts a regex in half and stops every combined script for visitors #2056), leaves every row at "Checking…" with no explanation.
• The device-ID collector is blocked. Tracker lists block the fingerprint library (uBlock with EasyPrivacy, Brave Shields, Firefox strict mode). The row then says "not available" as if the browser lacked something.
• The captcha only reports support. The row says whether the browser supports what the captcha needs, not whether the widget's script loaded.
• Requests to the server are never tried. Nothing checks that admin-ajax.php, the path every form submits through, answers.
• The copied results lack context. They do not say which plugin version or which settings the page ran with.

Acceptance criteria

• A notice rendered in the page, revealed by CSS after a delay and cancelled by the script when it starts, says the test could not run and why that may be. A <noscript> message covers JavaScript turned off.
• The device-ID row says the collector was blocked when the page asked for it and it did not load.
• The captcha row says when the captcha's script did not load on a page that uses it.
• A new "Server requests" row calls admin-ajax.php and shows OK with the response time, or that the request was blocked or failed.
• "Copy the results" adds the plugin version and the relevant settings: captcha mode, device limit, location on forms.
• If simple, a notice when the page's script is older than the plugin, which means it was served from a cache.
• Tests, the three catalogues, docs and the CHANGELOG are updated.