Use new json column for default branch protection

What does this MR do and why?

Use new json column for default branch protection

This commit adds the functionality to start using new json column for creating default branch protection instead of using the old integer column

EE: true

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Before	After

How to set up and validate locally

Use API put groups/:id to update default branch protection settings, when the feature flag is disabled use the below json body:

{
"default_branch_protection": 2
}

When the feature flag is enabled use the below json body:

{
"default_branch_protection_defaults": {
        "allowed_to_push": [
            {
                "access_level": 40
            }
        ],
        "allow_force_push": false,
        "allowed_to_merge": [
            {
                "access_level": 40
            }
        ]
    }
}

For the json values for each setting, you can refer to class https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/gitlab/access/branch_protection.rb?ref_type=heads

and call Gitlab::Access::BranchProtection.new(level).to_hash this will give you converted values from integer to json.

1. Enable feature flag: default_branch_protection_defaults
2. Change default branch protection setting using group put API
3. Create a project and check we have correct protected branches.

setting	feature flag disabled	feature flag enabled
Protection None
Protection Partial
Protected Fully
Protected Against Developer Pushes
Developer can initial push

Related to #408152 (closed)