revenue-distribution: add debt recovery for written off debt

[karl-dz]

This change implements RFC-0003, which outlines the ability to recover bad debt and to classify debt as erroneous.

One addition to this change is a field to the program config, which controls when debt can be recovered (number of epochs relative to the distribution's epoch). For example, if this field were to be configured to 2 epochs, written off debt for epoch 69 can only be recovered at epoch 71, which allows the debt account to reclassify debt during epochs 69 and 70.

This change also splits resolving bad debt into two separate instructions: reclassify and recover Solana validator bad debt. Because the two additional accounts felt awkward in the old resolve-bad-solana-validator-debt instruction (optional depending on whether debt is recovered), I modified the implementation (also reflected in the RFC).

I also refactored some of the processor logic to reduce code repetition. And I added new methods and modified existing methods for DoubleZeroEpoch and impl_unit_share to have const fn.

Some state interfaces changed, which necessitates a zero-versioned minor bump. Integrators on v0.1, however, will still be able to read the previous state variables.

No account migration needed with this change.

Closes malbeclabs/doublezero#2350.