feat: Adding new feature flag for the new node registration feature

[NikolaMilosa]

This is a temporary flag that will be used during the development of the More Secure Node (Re)deployment process.

Initially node providers will be able to opt in the feature (by providing enable_beta_registration_feature=true). This will give them flexibility to revert back to the old approach if the new approach has bugs.

When the feature is more stable, it will be enabled by default and providers will be able to opt out (by providing enable_beta_registration_feature=false). This will cover the cases where we notice bugs later during development process.

At the moment, the flag isn't used anywhere and in the following PR's will it be incorporated in the different parts of the stack.