This reverts commit 5ba542b1, reversing
changes made to 32c831ea.

This reverts commit ced005f3, reversing
changes made to 9b01b293.

Revert "Merge branch '44870-remove-extra-space-around-comment-form-on-merge-requests' into 'master'"

This reverts merge request !18120

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

Moves placeholders components into shared folder with documentation. Makes them easier to reuse in MR and Snippets comments

Reduced the technical debt around our JS flash function by making it a
module that is imported rather than relying on the global function.
The global function still exists mainly for technical debt with how
some requests are being completed, but new JS should import the module
directly.

Also reduces some tech debt in the file by removing the need for jQuery.
Instead Flash is now 100% vanilla JS.

Put back deleted tests