Support per-url enterprise configuration

[mrmonday]

Feature description

Enterprise configuration enables setting credentials using the windows registry for GCM.

GitLab support has settings which are per-url something like: credential.https://url.something.

Currently, enterprise configuration only supports settings in the form credential.something, not credential.https://url.something, which means for example, multiple gitlab instances cannot be configured at the enterprise level.

It looks like support for this is implemented here: https://github.com/GitCredentialManager/git-credential-manager/blob/9ecda7b84778f89de6356c9b3fa47a7587c5ab5f/src/shared/Core/Settings.cs#L420-L424 - it probably just needs a similar block slightly further up in that method.

[mjcheetham]

This was merged in #1149 and will be included in the next GCM release.