[Rebalancing] [Part4] Compute depositories target weights IX

[crypto-vincent]

PR Combo:

• uxd-client: https://github.com/UXDProtocol/uxd-client/pull/40
• uxd-program: https://github.com/UXDProtocol/uxd-program/pull/241

This PR introduces:

• a new IX: compute_depositories_targets
• 2 new fields for credix/mercurial depositories:
  • redeemable_amount_under_management_weight // manual static arbitrary weight desired for the depository
  • redeemable_amount_under_management_target // absolute amount depending on the weight, cap and total supply

The goal of this new compute_depositories_targets IX the following:

• uses all depositories redeemable_amount_under_management_weight
• uses the current total supply and all depositories caps
• then compute the new absolute redeemable_amount_under_management_target for all depositories

The idea is that the amount in redeemable_amount_under_management_target of each depositories will then be used as an informatory value used during computing rebalancing amounts later (this amount can fluctuate over time, rebalancing can be lagging a bit in time without any problem)

[crypto-vincent]

This PR is now deprecated, another PR is going to be used in its place: https://github.com/UXDProtocol/uxd-program/pull/249