increased perf of scrolling tabs into view

spec fixes

[ci skip]

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scroll to the active tab when opening/closing

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removed old store, helper & monaco loader
moved monaco loader into editor component because it is the only
component that requires monaco

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removed an ID from the CSS

clears all tmp files after cancelling edit mode

specs

Closes #38614

fixed previous directory showing when it shouldnt

fixed eslint

This moves away from storing in a single array just to render the table.
It now stores in a multi-dimensional array/object type where each entry
in the array can have its own tree. This makes storing the data for
future feature a little easier as there is only one way to store the
data.

Previously to insert a directory the code had to insert the directory
& then the file at the right point in the array. Now the directory
can be inserted anywhere & then a file can be quickly added into this
directory.

The rendering is still done with a single array, but this is handled
through underscore. Underscore takes the array & then goes through
each item to flatten it into one. It is done this way to save changing
the markup away from table, keeping it as a table keeps it semantically
correct.

Fix
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12198#note_37147332

Fix
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12198#note_37143794

[ci skip] WIP dynamically switch between preview and repo-editor, disable edit button and editor for binary files