Clean up ClipboardJS instances from focus management workaround

[afercia]

See related issue and PR on the Gutenberg editor repository:
​https://github.com/WordPress/gutenberg/issues/57154 and ​https://github.com/WordPress/gutenberg/pull/57156

ClipboardJS used to suffer from a bug that triggered a focus loss. Over time WordPress implemented its own workaround to avoid this focus loss. The issue was also reported upstream at ​https://github.com/zenorocha/clipboard.js/issues/680

ClipboardJS 2.0.11 includes a fix for this focus loss issue so that the workaround used by WordPress is no longer necessary.
Reference:
​https://github.com/zenorocha/clipboard.js/releases/tag/v2.0.11
​https://github.com/zenorocha/clipboard.js/pull/807

Given that Core already uses ClipboardJS 2.0.11 since a while, we can now clean up all the related code for all the 'Copy' buttons in the codebase.

[paulkevan]

@afercia had trouble attaching the diff (see: ​https://wordpress.slack.com/archives/C02QB8GMM/p1703242790604879) hence, why I added it.

[afercia]

Test instructions for 60139.diff​

Test the patch in a couple places where there is a 'Copy' button for example:

• Go to Tools > Site Health > Info
• Use the keyboard to move focus to the 'Copy site info to clipboard' button.
• Activate the button by pressing the Enter or Spacebar keys.
• Observe focus stays on the button.
• Go to Media > List view
• Move focus to one of the attachments 'Copy URL' button in the Quick actions.
• Activate the button by pressing the Enter or Spacebar keys.
• Observe focus stays on the button.
• Go to Media > Grid view
• Open one of the attachments modal dialog details.
• Move focus to the 'Copy URL to clipboard' button.
• Activate the button by pressing the Enter or Spacebar keys.
• Observe focus stays on the button.

[dhrumilk]

Test Report

Environment

• 12th Gen Intel(R) Core(TM) i5-1240P 1.70 GHz
• Chrome 120.0.6099.111
• Server: nnginx/1.25.1
• PHP: 7.4.33
• WordPress:6.5-alpha-56966-src
• Theme: 1.3 Twenty Twenty-Three (twentytwentythree)

Test Results

working as expected.

After the patch-
​http://tinyurl.com/ytr6oc7o

[afercia]

In 57231:

External Libraries: Accessibility: Clean up clipboard.js Copy buttons from focus management workaround.

clipboard.js used to suffer from a bug that triggered a focus loss when activating the Copy buttons. The bug was fixed a while ago with the clipboard.js 2.0.11 release so that the workaround implemented in WordPress is no longer necessary.

Props dhrumilk, paulkevan, afercia.
Fixes #60139.