Bad handling of too large Snippet files

Summary

When creating a Snippet that is a) too large file, or b) has too many lines, the handling is far from being optimal. This is a regression after refactoring Snippet view to Vue

Before refactoring	After refactoring

⚠ The scope of this Issue has been re-defined and can be found in detail in the relevant BE issue.

Steps to reproduce

• Create a new Snippet with too many lines (some .log or .eslintcache should be fine)
• The view will simply tell collapsed or too_large without a possibility to get to the snippet's content

Example Project

Reproducible on gitlab.com

What is the current bug behavior?

There's no way to get to snippet's content

What is the expected correct behavior?

It should be possible to either load the content anyway or download the snippet.

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)