Add Allow custom account name to Varbase general settings to work with Email Registration ~2.0.0

Problem/Motivation

#3399770: Update Email Registration module from ~1.0 to ~2.0.0

Steps to reproduce

Given that a user with a permission to "Administer users"
And the new Email Registration ~2.0.0 was in the system
When the user add or edit users
Then the Email Registration module will not Allow custom account name

Proposed resolution

• Add Allow custom account name to Varbase general settings
• Add schema for Varbase Core settings configs
• Have a hook update to set Allow custom account name as True for old sites ( Same config as in old Email Registration ~1.0

Remaining tasks

• ✅ File an issue about this project
• ✅ Addition/Change/Update/Fix to this project
• ✅ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support on feature change/addition
• ➖ User Guide Documentation support on feature change/addition
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ✅ Code review from 1 Varbase core team member
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Update Release Notes and Update Helper on new feature change/addition
• ✅ Release varbase-9.0.17, varbase_core-9.0.75, varbase-9.1.0,varbase_core-9.1.10, varbase-10.0.0-rc1, varbase_core-10.0.0-rc9

Varbase update type

• ✅ No Update
• ➖ Optional Update
• ➖ Forced Update
• ➖ Forced Update if Unchanged

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• Issue #3399834: Added "Allow custom account name" to Varbase general settings to work with Email Registration ~2.0.0