The config.js now accepts a new boolean flag. When defined, it sets
a global property using the Vue Global API. The components
GlDisclosureDropdown and GlCollapsibleListbox now use a mixin
which is setting a property, and a computed property, using either
the property, falling back to the global property (secondary).

Resolve "Add global var to config, and use it in DiscloreDropdown and Listbox"

Closes #2798

See merge request !4444



Merged-by: Paul Slaughter <pslaughter@gitlab.com>
Approved-by: Mark Florian <mflorian@gitlab.com>
Approved-by: Paul Slaughter <pslaughter@gitlab.com>
Reviewed-by: Mark Florian <mflorian@gitlab.com>
Co-authored-by: Vanessa Otto <votto@gitlab.com>

# [87.7.0](v87.6.1...v87.7.0) (2024-08-01)

### Features

* Add boolean flag for improvedHideHeuristics in Config ([1fa70373](1fa70373))