Introduces the faux primitive capability `view_site_health_checks` available to single site admins and multisite super-admin to view the site health page within the admin.
The capability is mapped to the `install_plugins` capability without being dependent on the file system being writable. This fixes a bug where the feature couldn't be used by sites unable to write to the file system or managed through version control.
The capability is granted on the `user_has_cap` filter.
Props birgire, Clorith, palmiak, peterwilsoncc, spacedmonkey.
Fixes#46957.
git-svn-id: https://develop.svn.wordpress.org/trunk@45507 602fd350-edb4-49c9-b593-d223f7449a82