This commit introduces the internal accounting logic for accrueing
multiplier points, that will later be used to determine how many
experience points an account is eligible to.
The majority of the work here was done by @3esmit.
This is actually a bug that the certora prover found.
The rule `epochStaysSameOnMigration` failed because a previous
`StakeManager` could call `migrationInitialize` and change
`currentEpoch` on a next `StakeManager`, even though the next `StakeManager`
might be in migration itself (which means the `currentEpoch` is now
allowed to change).
This commit fixes this by ensure `migrationInitialize()` will revert if
the `StakeManager` already has a `migration` on going.
Since we're implementing rules for `StakeManager` migrations, we need
multiple instances inside the certora specs.
This results in the prover trying to run rules on the other
`StakeManager` instance as well, which isn't always desired,
as it causes some rules to fail, even though they'd pass if they'd be
executed only on the `currentContract`.
This commit makes the filter condition for relevant rules stronger, such
that the prover will not run them on the `newStakeManager` contract
instance.
There have been a bunch of breaking changes in the staking contract that
resulted in our specs not compiling.
This commit fixes this, however it does not yet ensure the prover is
satisfied.