Adds rel="noopener noreferrer" to all links with target="_blank"

See merge request !2071

Removes `:visible` from selector
Adds CHANGELOG entry
Removes iife

See https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9245

unbind existing listenerss and remove duplicate MiniPipelineGraph init

There were two problems here:

1. On the JS side, the reference to $widgetBody didn't refer to the
   right DOM element any more. This might be because it was replaced by
   the `getMergeStatus` method. Even if it wasn't, ensuring we have the
   right element means that the content gets updated.

2. On the Ruby side, the `log_merge_error` method didn't update the
   `merge_error` column of the merge request. Change that to update if
   requested, and update in the most common cases by default.

   Additionally, this would sometimes return an error hash, but it
   doesn't look like this was ever used (the return value of
   `MergeService#execute` appears to be unused everywhere).

Closes #27948

Added tests

review changes

Fix specs

expand remaining non-explicit eslint-disable blocks and factor out globals when no-undef encountered

Added hiddenInterval and immediateExecution settings, fixed visibilitychange listening, implemented with mr widget

Updated tests

Added tests

Review changes