As decided in https://gitlab.com/gitlab-org/gitlab-ce/issues/53593

Pass string value in through haml template data attribute
Evaluate it into a regex when initiating variable list
Use it to determine whether to show the maskability warning

Set the default value to false
Adjust tests to expect false as the default
Update documentation to make new default clear

In addition to API, add support for toggling mased on UI too.

(Though fabricate_via_browser_ui is private)

Adds custom-select class to the select menu for variables
type in CI/CD settings

For the variables list in CI/CD settings
this commits adds an header row with titles

Add env_var and file as supported types for CI variables. Variables of
type file expose to users existing gitlab-runner behaviour - save
variable value into a temp file and set the path to this file in an ENV
var named after the variable key.

Resolves https://gitlab.com/gitlab-org/gitlab-ce/issues/46806.

Update error message "This variable will not be masked" to
"Cannot use Masked Variable with current value"
Add link to masked variables section to error message

Show masked switch for each variable
When toggled on, the variable value will be masked in runner logs
Show warning message if the switch is on but the value is not maskable

This reverts merge request !25476

Add a masked switch to variable rows
Copy some behavior from the protected switch

Add hint about adding variables for Auto DevOps application variables
and link to More information

also remove debug

The problem of using .js-ci-variable-input-value is that,
whenever the value is hidden, then this selector won't be set,
instead, .js-secret-value-placeholder would be set.

If we just fill the value, the value is revealed. But if
we visit this later, the values were be hidden. This means
we don't have a consistent way to count the values.

Adding an unique qa selector to both revealed and hidden
values would make it easier to track the values.

To make it look more consistent, let's also do the same
for the key.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/42928

See https://gitlab.com/gitlab-org/gitlab-ce/issues/39118

Conflicts:
	app/views/ci/variables/_form.html.haml
	app/views/ci/variables/_table.html.haml
	ee/app/views/ci/variables/_environment_scope.html.haml
	spec/javascripts/ci_variable_list/ci_variable_list_ee_spec.js
	spec/javascripts/fixtures/projects.rb

Part of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4110

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/38019