Adds tests that adds new files via file templates via the Files view
and the Web IDE.

Includes changes to page objects and associated code

Fetches template content from the API rather than hardcoding strings
that will need to be updated if the templates change. Some of the
content is stored as flat files but we can't use them because they're
not included in the docker images gitlab-qa uses.

Closes #47307

The blue shortcut commit button opens the commit interface to
actually perform the commit. The ellipsis indicates the button doesn't
immediately perform the commit.

fixed form collapsing too soon

instead of taking over whole sidebar, it now just shows over the commit box
after 5 seconds the commit box goes back to its compact logic

remove object.assign instead directly assign to state
created new constants

remove close button in tab
fix height not working in form
restored stage & unstage all changes
disable merge request radio button when staged & unstaged changes exist

update lastOpenedAt for pending files