Fix scroll bars shown in Revert dialogue box
## What does this MR do?
Eliminate scroll bars shown in Revert dialogue box, see the screenshots.
## Are there points in the code the reviewer needs to double check?
N/A
## Why was this MR needed?
Ugly scroll bars are shown in Revert dialogue box.
## What are the relevant issue numbers?
N/A
## Screenshots

See merge request !3532
Standardize the way we check for and display form errors
- Some views had a "Close" button. We've removed this, because we don't
want users accidentally hiding the validation errors and not knowing
what needs to be fixed.
- Some views used `li`, some used `p`, some used `span`. We've
standardized on `li`.
- Some views only showed the first error. We've standardized on showing
all of them.
- Some views added an `#error_explanation` div, which we've made
standard.
See merge request !3531
Updated UI for new merge request
Closes#2540


See merge request !3228
Ignore toggling the sidebar for resolutions over 1200px width
Closes#14353

See merge request !3547
Only load emoji spritesheet when necessary
On a normal issue where the only award emoji displayed by default are
the thumbs-up and thumbs-down emoji, this decreases the page load by
670KB or 250KB depending on pixel density.
Resolves#14334.
See merge request !3449
The emoji_icon helper used to display the award emoji in Issue and
Merge Request views. By default the spritesheet is used, but passing
`sprite: false` to the `emoji_icon` helper makes the emoji render as
separate images.
For award emoji displayed by default (e.g. thumbs-up, thumbs-down, and
any that have been awarded to the issue/MR) the independent images are
used. Only when the full emoji menu is opened does the full spritesheet
load.
On a normal issue this change decreases the page load by 670KB or 250KB
depending on pixel density.
Resolves#14334.