Move settings definition on contribution settings form to metadata.

[eileenmcnaughton]

Overview

This moves the code that allows settings to be added to forms by metadata from the Generic setting form to the setting trait.

This means many more forms will support injecting settings by metadata. Specifically we switch across the Contribution preferences form,
making credit_note_prefix a metadata-added field. This is preliminary to moving that to an extension & allows us to inject it
in by simply defining the metadata in a hook

Before

Hard coded settings on form

After

Setting spec for adding settings to form used & respected

Technical Details

Pre the setting spec the preferred way to add a setting to a setting page is through metadata
-ie
'settings_pages' => ['contribute' => ['weight' => 80]],

Note that some pages are fully converted to the extent there is no actual php class for them - this doesn't do that :-) - It allows settings to be added by metadata to non fully converted forms

Comments

Credit notes prefix is pulled out of the invoicing section and into the metadata-defined section - as disabling invoicing does not enable the credit not prefix usage

[civibot]

(Standard links)

• If this is your first pull-request for CiviCRM, please browse CONTRIBUTING.md for information about the development and testing processes.
• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).

[mattwire]

Before, settings. After, settings.