Add icons and buttons to UI guide

cc @jschatz1 @skyruler 

See merge request !4445

Fix import error handling

Fixes https://gitlab.com/gitlab-com/support-forum/issues/745

This improves import error handling:
- Now if there's an error during importing before the job is scheduled, we also mark the project status as failed.
- Refactored setting the status to failed into one single method.
- Fixed some situations where the error message was missing or simply empty.

See merge request !4366

See merge request !4436

Add tooltips to todo target links



See merge request !4370

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This will be useful when you want to ask for the 
number of items and later iterate over them, without 
needing to ask if the association is load or not.

So you avoid extra database queries

[ci skip]

Fixes missing number on generated ordered list

Closes #18102 

See merge request !4437

Reduce number of fog gem dependencies

Currently supported:

* AWS
* Azure
* OpenStack
* Google
* local storage

Closes #15352

See merge request !4396

Cache project build count. Closes #18032

See merge request !4377

Move feature specs for shortcuts to valid directory

This MR moves tests to valid directory that matches our namespace we use in code.

See merge request !4433

Cache assigned issue and merge request count. Closes #18036 and #18035

See merge request !4378

Clicking search pill focuses field

When clicking the pill in the search field, it now focus the field. Previously you would have to make sure you click in the field.

Fixed an issue where clicking out of the field wouldn't remove the focus
outline

Also reduced some of the HTML to remove what isn't needed

See merge request !4279

Fix serious performance bug with rendering Markdown with InlineDiffFilter

Nokogiri's `node.replace` was being unnecessarily called for every text node in
the document due to a comparison bug. The code previously was comparing the
HTML representation of the full document against the text node, which would
always fail. Fix the comparison to just compare the modified text.

Closes #18011 


See merge request !4392

Fix link to blank group icon

When the group is the default blank icon, this needs to use the
`image_path` helper; otherwise, the link won't work if assets are
precompiled. This still works fine for uploaded icons in either case.

Closes #14446.

See merge request !4375

Fix wiki project clone address error

_Note: Originally opened at !4407 by @chujinjin._

---

fix wiki project clone address error in Wiki Git Access View, show as below:

![image](/uploads/5e3bf6d1418c42862a885319c31bc3cf/image.png)

Fixes #17643.

See merge request !4429

When the group is the default blank icon, this needs to use the
`image_path` helper; otherwise, the link won't work if assets are
precompiled. This still works fine for uploaded icons in either case.

Minor doc updates

## What does this MR do?

Adds to and clarifies some documentation. Specifically, when using `gdb` to debug you need to detach and exit when done. Next, this clarifies the type of file locking that we require.

Thanks to @northrup for the details about mandatory vs. advisory file locking.

Note: These were two really small changes so I combined in to one merge request. However, I left the commits separate for clarity.

See merge request !4421

Nokogiri's `node.replace` was being unnecessarily called for every text node in
the document due to a comparison bug. The code previously was comparing the
HTML representation of the full document against the text node, which would
always fail. Fix the comparison to just compare the modified text.

Closes #18011

Load d3 only when necessary

Now d3 is only loaded on the users' show page and the graphs pages, where it's necessary.

Redo of !3993.

This decreases page size from 4.6MB to 4.3MB for a given Activity page (before compression), or a savings of 300KB. This is essentially a proof of concept for removing larger dependencies such as the Ace Editor, Chart.js, and Raphael, which will likely provide another 1MB of savings on most pages (again, before compression).

See merge request !4394

Remove Coveralls and Semaphore badges. [ci skip]

Remove Coveralls and Semaphore badges from the README. They're outdated,
unused, and not GitLab CI :)

[ci skip]

See merge request !4334