[Teonite-External] Precursor changes to data structures for reserved delegator slots change in future.

[devendran-m]

Please make sure relevant breaking changes to data structures are in place for the 2.0.0 / Cndor release. This allows us to avoid introducing breaking changes in a future release that includes the full implementation of the reserved delegator slots functionality.

Changes - To add:

• ValidatorBid::reserved_slots field to track number of reserved slots (defaulted to 0)
• add_reservations and cancel_reservations auction contracts with stubbed implementations
• struct Reservation to track reservations
• BidKind::Reservation(Box<Reservation>) and BidKindTag::Reservation variants
• BidAddr::Reservation and BidAddrTag::Reservation variants
• TransactionEntryPoint::{AddReservations, CancelReservations} variants
• auction costs for add/cancel reservations ops

Please note that this issue is created retrospectively, for the PR #4775

[devendran-m]

Closed as the related PR #4775 is approved and merged.