Add ability to edit Group Approval Rules at the Project level

The first iteration of group approval rules should allow editing of group level rules at project level, but only to increase the number of approvals required for a group level rule.

It shouldn't be possible to reduce required approvers or edit who can approve or to make group level rules more permissible.

To achieve this in the backend we will likely mirror how project rules are overridden at MR level, by copying the ApprovalGroupRule attributes to a new ApprovalProjectLevel rule and store the relationship in a new table approval_project_rule_sources.

Todo:

1. Add the table approval_project_rule_sources and model ApprovalProjectRuleSources to store the relationship between ApprovalGroupRules and ApprovalProjectRules.

2. Update ApprovalRules:CreateService and ApprovalRules::UpdateService to support editing of Group approval rules at project level.

See &11451 (comment 1747834662) for more details.