core: Scoped Configuration Sources

[krantzinator]

Waypoint has supported dynamic configuration for some time. This enables users to supply configuration from a given config sourcer plugin to their application config, or with dynamic defaults set for input variables. There is a limitation of this, though - for a given config sourcer plugin, only the global scope is supported. In practice, this means that all projects and applications within a single Waypoint server, in all workspaces, will source their configuration for a config sourcer plugin from the same source.

Waypoint can be improved to support scoped configuration sources. Scoping is supported with other features of Waypoint, including application configuration, and can be applied to configuration sources as well. “Scoping” here means that for a given project or application “scope” in a given workspace, or all workspaces, dynamic configuration can be read from a single configuration source specific to that scope.

[krantzinator]

Fixed with #4196 and #4191