Trigger autosize update after template selection
## What does this MR do?
Triggers an autosize update after selecting an issue template.
The autosize plugin doesn't react to value changes and therefore doesn't automatically update when the user selects the template. This merge request adds it so that it detects if the editor the template selector is a jQuery object (not Ace editor) & then triggers the autosize event to allow the user to scroll the textarea.
## Screenshots (if relevant)
![resize](/uploads/1ab04b4202309b13f1178e04c0953112/resize.gif)
## What are the relevant issue numbers?
Closes#21982
See merge request !6282
Prior, the value of the Ace editor was only being persisted if the user
physically clicked the submit button, which the "quick submit" behavior
doesn't do.
Now the value will be properly transferred before any form is submitted.
Change "+" icon under "Files" section to have three options:
* Create file
* Upload file
* New directory
Upload file is no longer accessible from the "Create file" page.
Users can now select a target branch in upload file as well.
Closes#2799: Fixes a bug where file modes were overwritten after a commit
Closes https://github.com/gitlabhq/gitlabhq/issues/8253: Existing files
can no longer be overwritten in the "Create file" section.
Closes#2557
Dynamically adjust placedholder for uploads and fix Dropzone event handlers
Override error handler to prevent error messages from being inserted underneath image preview
Fix tests
Use regexp instead of startsWith for better browser compatibility
Remove duplicate code in _replace.html.haml and use one template
Remove files upon error and retain alert messages until user adds a new file
Refactor upload and replace functionality
Rename file and move CSS
Fix typo
Make dropzone a div
Remove unnecessary file
Change color of "upload existing one"
Add missing changes