Remove target=_blank from links in media settings forms

From media module configuration:

• Removed target="_blank" from these links, and the "opens in new window" text.
• Also changed sentences on MediaSettingsForm.php and OEmbed.php file.

I'll be working on test case fail issue.

Hey,
There is one minor change I forgot to update in my last patch #8. There was two `.` at last.

--- a/core/modules/media/src/Plugin/media/Source/OEmbed.php
+++ b/core/modules/media/src/Plugin/media/Source/OEmbed.php
@@ -301,7 +301,7 @@ public function buildConfigurationForm(array $form, FormStateInterface $form_sta
     $domain = $this->configFactory->get('media.settings')->get('iframe_domain');
     if (!$this->iFrameUrlHelper->isSecure($domain)) {
       array_unshift($form, [
-        '#markup' => '<p>' . $this->t('It is potentially insecure to display oEmbed content in a frame that is served from the same domain as your main Drupal site, as this may allow execution of third-party code. <a href=":url" target="_blank">You can specify a different domain for serving oEmbed content here</a> (opens in a new window).', [
+        '#markup' => '<p>' . $this->t('It is potentially insecure to display oEmbed content in a frame that is served from the same domain as your main Drupal site, as this may allow execution of third-party code. <a href=":url">You can specify a different domain for serving oEmbed content in the Media settings.</a>.', [
           ':url' => Url::fromRoute('media.settings')->setAbsolute()->toString(),
         ]) . '</p>',
       ]);

I'm updating it in this latest patch.

Removed the changes from the field widgets.

Huge +1 to this. I noticed this a couple weeks ago and had actually meant to file an issue. Glad someone else did.

These two remain:

media.module:    $elements['#media_help']['#media_add_help'] = t('Create your media on the <a href=":add_page" target="_blank">media add page</a> (opens a new window), then add it by name to the field below.', [':add_page' => $add_url]);
media.module:      $elements['#media_help']['#media_list_link'] = t('See the <a href=":list_url" target="_blank">media list</a> (opens a new window) to help locate media.', [':list_url' => $overview_url->toString()])

Both explicitly say that a new window will be opened, so I think that meets the a11y requirement.

One thing for @pradeepjha and @Sivaji: In the future, please provide interdiffs for your patches. That allows reviewers to evaluate your changes. Thanks!

Since this is a string change, it unfortunately just missed backport to 9.0 and 8.9. I considered backporting it anyway, but unfortunately the tradeoff of changed strings is that many users would not be able to read any of the message, which would be worse than this accessibility bug I think. But it is in 9.1.x.

I think there should be a sniff to warn devs about target="_blank", so tagging for a followup. Thanks!